FX drama “The Strain” has delivered impressive ratings since its Sunday night premiere, emerging as the biggest new cable drama in young adults this summer and perhaps the biggest ever for the network. But a bigger story is that it took FX this long to tout its performance.

In a first for a TV industry grappling to get an accurate handle on audience measurement in the DVR era, the network waited until Nielsen issued its “Live + 3” numbers on Friday to release any ratings data to the press. The “Live + Same-Day” numbers were issued by Nielsen on Tuesday, and reported in some outlets, but they are increasingly becoming irrelevant for a business whose chief advertising currency is sold off numbers that include three days’ worth of DVR playback.

It’s not unusual these days, especially for 10 p.m. dramas like “The Strain,” to jump in rating by more than 50% with just three days’ worth of DVR playback. (The young-adult audience for “Strain” actually swelled by 64%, and could come close to doubling its audience when a full week’s worth of data is included.)

“With the exception of sports, news and live events, Live+Same Day ratings no longer accurately reflect the audience delivery for a scripted entertainment program,” said FX’s John Solberg in a note accompanying Friday’s ratings release. “We believe they grossly mischaracterize the actual audience due to the multiple data streams and platforms. Therefore, our first acknowledgement of any ratings will be on a Live+3 basis and beyond.”

It may prove more difficult for the broadcast networks to do this, as there is a decades’ long tradition of making next-morning ratings judgments about their shows, but FX is hoping its new ratings policy can at least spur a discussion throughout the industry.

Looking at Guillermo del Toro’s vampire-virus drama”The Strain,” it averaged a 1.91 rating in adults 18-49 (2.43 million viewers) and 4.73 million total viewers in “Live + 3” ratings, rising 64% in demo rating (from 1.18) and 58% in total viewers (from 2.99 million) from its “Live plus same-day” averages. The 1.91 puts it ahead of TNT’s “The Last Ship,” which did a 1.73 rating in Live+3 (after earning the same 1.18 rating as “The Strain” in “Live+same-day”).

When Live+7 data is released by Nielsen, “The Strain” figures to leap-frog “The Americans” (5.12 million total viewers) to become FX’s most-watched drama ever by this measure.

FX also projects that, inclusive of Live+7 data, VOD, digital and electronic purchases, the series premiere of “The Strain” will deliver over 10 million total viewers.

“The Strain,” from FX Productions, was co-created and is executive produced by Guillermo del Toro and Chuck Hogan, who teamed to pen the pilot script. Del Toro directed the episode.

Carlton Cuse serves as executive producer/showrunner and writer. Gary Ungar also serves as executive producer.

Showtime also issued Live + 3 numbers for its Sunday series on Friday, though it’s unclear if this will be an ongoing policy. Its “Ray Donovan” and “Masters of Sex” had looked soft in their second-season premieres when the same-night numbers were released by Nielsen on Monday, but looked healthier four days later.

“Donovan” jumped 52% from same-night (1.224 million) to L+3 (1.865 million) to virtually match the 1.9 million for its year-ago series premiere. “Masters” surged by 68% (825,000 to 1.387 million) and also was in line with its series premiere of last year.

Both shows enjoyed stronger lead-ins for their series premieres (“Ray Donovan” had “Dexter” and “Masters of Sex” had “Homeland”), so holding steady is a positive sign.