Amazon’s Kindle products are some of the most popular e-readers around, but there’s a price to pay for the convenience of Amazon’s huge library and convenient syncing features: the company appears to be tracking, recording, and storing data on every single tap you make on the device. The extent of the tracking was brought to light in a tweet by Adrianne Jeffries, an investigative reporter for The Markup (and friend of The Verge) earlier this week.

That just left the question: why is Amazon tracking such granular data in the first place?

Amazon appears to be tracking every tap on Kindle. I just got my data back and there are 90K rows of this pic.twitter.com/wVCSXCTVwv — Adrianne Jeffries (@adrjeffries) January 28, 2020

It turns out that Amazon has a few answers to that, some more convincing than others. The main feature Amazon claims it needs the data for is the Kindle’s “Whispersync” functionality that allows for a reader to sync their exact place in a book between different devices, along with notes, highlights, and bookmarks. By tracking when you turn pages and which books you’re reading, Amazon says it can properly track where you are in a book and keep that data in sync. Amazon also says it uses the specific data here to power its “Reading Insights” features for tracking reading goals and celebrating milestones (sort of like fitness tracking, but for reading).

A more compelling answer is that Amazon uses insights from the data it collects to improve the Kindle software as a whole. “For example, we noticed that readers were tapping pages backwards and forwards in frequent succession, likely trying to flip back and forth between pages and reference different parts of a book. To address this, we have built several navigation features, including Page Flip and the ability for customers to continuously scroll through their book when reading.”

As for the actual data itself, Amazon wouldn’t tell us specifically how long it maintains the logs, but says that it keeps the data “as long as it is needed to fulfill the purposes described in our Privacy Notice, to comply with relevant laws (including for tax and accounting purposes and to protect our customers from fraud) or as otherwise communicated.”

If you don’t want Amazon to collect your data on every tap you input on your Kindle, there are two options: you can request that Amazon delete the existing data it has recorded and you can opt out of future collection of your reading data by going into Kindle settings and disabling Whispersync. Unfortunately, Whispersync is a pretty major feature to lose if you’re someone who uses multiple devices to read, but if the tracking is as central to the feature as Amazon says it is, it’s a choice you’ll have to make.