Shares of cloud storage provider Box tanked more than 10 percent Wednesday morning after the company reported earnings for the second quarter of its 2019 fiscal year and offered slightly weak guidance for the third quarter.

The stock fell as low as $23.53, extending its after-hour losses on Tuesday. That puts Box on pace for its worst day since March.

The company's quarterly report revealed slower billings growth, according to analysts for Rosenblatt, adding uncertainty to the second half of the year.

"Customers have been telling us over the past few months that it has gotten easier to do business with the company, with more deal standardization and better access to technical resources," Rosenblatt said in a note. "However, it's become clear to us that the company still has at least another two quarters of product rollout and sales ramping before it will be able to fully capitalize on these factors."

Here's how Box did in its second quarter, which ended July 31:

Earnings: Loss of 5 cents per share, excluding certain items, vs. loss of 6 cents per share as expected by analysts, according to Thomson Reuters.

Loss of 5 cents per share, excluding certain items, vs. loss of 6 cents per share as expected by analysts, according to Thomson Reuters. Revenue: $148.2 million, vs. $146.5 million as expected by analysts, according to Thomson Reuters.

The company narrowed its loss from 11 cents per share, excluding certain items, and grew revenue by 20.6 percent, according to a statement. There were 11 deals worth more than $500,000 in the quarter, up from eight in the year-ago quarter, Box CEO Aaron Levie told CNBC on Tuesday.

Executives are forecasting that in the fiscal third quarter, Box will report a loss of between 8 cents and 7 cents per share, excluding certain items, on $154 million to $155 million in revenue. That's a little worse than what analysts were looking for: Expectations were for a loss of 6 cents per share, excluding certain items, on $155 million in revenue in the fiscal third quarter, according to Thomson Reuters.

Box slightly updated its guidance for the full 2019 fiscal year. It's now expecting a loss of 18 cents to 16 cents per share, excluding certain items, on $606 million to $608 million in revenue. That's in line with analysts' expectations of 18 cents per share, excluding certain items, on $606.5 million in revenue, according to Thomson Reuters.

In the past few quarters Box had been focused on increasing the amount of revenue it generates from each of its customers. Executives have recently said they were looking to achieve a $1 billion revenue run rate by the second half of its 2021 fiscal year. On a conference call with analysts on Tuesday, Box's chief financial officer, Dylan Smith, said executives don't want to identify a particular quarter when the company will pass that threshold. But Smith did say that executives "remain committed to surpassing a $1 billion in revenue for the full year of fiscal 2022."

Box's stock fell some more after those remarks.

Levie further addressed the targets on the call, emphasizing that the company will no longer say when it will hit the $1 billion run rate figure.

"What we're really not doing is just specifying the quarter in which we expect to cross that," Levie said. "Certainly in the second half that's completely possible. What we're trying to do is avoid too much focus on the specific quarter in which we cross that revenue threshold. Obviously, again, things like the seasonality and deals, puts and takes, in terms of the solution sales and add-on products -- we are moving back from the specific quarter that we've been talking about the growth rate."

Analysts have been focused on the growth that lies ahead over the next few years.

"While recent go-to-market initiatives should help drive improved revenue per customer trends in the out years, we believe concern over Box's ability to reach this objective remains an overhang on shares," Raymond James analysts led by Brian Peterson wrote in a Monday note.

Changes to salespeople's compensation plans that are meant to encourage larger deals are having their desired effect, Rosenblatt Securities' Marshall Senk wrote in a Friday note. There are also more deals involving multiple products in Box's pipeline, Senk wrote.

"It's still early, because of just the amount of time it kind of takes to ripple through the entire sales organization, so we're still seeing some segments in the business kind of still have to kind of catch up to this transformation, but we're seeing great growth in ... the number of big deals, which is a really key metric of this transformation," Levie told CNBC. Two-thirds of deals worth more than $100,000 in the quarter included new Box products, Levie said.

The company now has more than 87,000 business customers, up from more than 85,000 one quarter ago.

Box stock is up 27 percent since the beginning of the year.

— CNBC's Josh Lipton and Sara Salinas contributed to this report.