11% conversion rate increase from a "Commitment Checkbox"

Oddly, their popup/lightbox (asking me "Did you enjoy this article? Sign up for our newsletter!") that blocked the entire page when I was halfway through reading the article caused me to click the button to convert right off of the page.

11% increase from landing page to application or did the conversion rate increase off the application page?

If it's 11% conversion increase off the application page, wouldn't conversions increase naturally because of the fact that you're filtering more people from the landing page?

"This checkbox alone, with that particular title, helped increase their successful application conversion rate by over 11% – an increase of hundreds more applications a month!"

Sounds like it is off the application page, but if the wording is to be believed this is a net increase.

"Conversion rate drops to 0 when you pop up something in front of the user while they're trying to read"