I don't have access to my device right now, but here is the the link which contains a screenshot:
https://github.com/Hagb/decryptBooxU...ment-894760534
I am not sure how much margin there supposed to be. The same layout is in the recovery mode, by the way

So I guess it starts right at the first pixel, being a barebones system (I mean, "it says supported API:3" which is even pre-Android 1.5...)
Also, in KOReader both top and bottom progress bars fall victims to this cropping as well