CBS has put “Under the Dome” under a microscope and discovered millions of new viewers for the summer hit.

The Eye on Thursday released detailed figures on how many — and how — viewers watched the first episode of the series, based on a Stephen King book, about a small town trapped under a mysterious dome. And it now appears that since the pilot first premiered June 24 on CBS, more than 20 million people have watched the show via multiple platforms.

Starting from the same-night audience Nielsen reported for “Under the Dome” on June 25 (13.53 million) — which already qualified the program as the most-watched summer drama premiere on television in more than 20 years — the show added 4.23 million viewers in Nielsen’s Live +7 data (DVR playback within a week of a premiere).

Video-on-Demand transactions through the first 22 days delivered an additional 1,605,513 viewers, according to Rentrak, while 22 days of viewership from online streaming on CBS.com and its multi-channel video partners added 484,542 viewers, based on CBS Interactive internal data.

That gets the total up to 19.85 million unduplicated viewers and still does not include viewership from Amazon’s Prime Instant Video, which provides exclusive online subscription access to all episodes of “Under the Dome” four days after the broadcast on CBS.

Amazon may not have released specific streaming figures, but it says the first episode of “Dome” was the most-watched TV premiere in the history of the service — meaning the show’s first episode has easily surpassed the 20-million viewer mark.

Detailed demo information is not available on non-linear platforms, but via seven days of DVR playback, the premiere of “Under the Dome” surged 1.3 ratings points in adults 18-49 (4.6 from a same-night 3.3) and 1.6 ratings points in adults 25-54 (6.1 from 4.5).

The networks know that there is a lot of viewing done via non-linear platforms and are certainly frustrated that so many viewers go uncounted. Nielsen is working on ways to incorporate more detailed ratings snapshots, but until then the networks are taking it upon themselves to do the legwork.

In February, Fox provided a similar viewership snapshot of its January drama premiere of “The Following.” That show started with a same-night audience of 10.42 million and swelled to 20.34 million unduplicated viewers once its on-air encore, seven days of DVR playback, VOD and streams on Fox.com and Hulu were all included.