When I download a file under android and calculate the progress of the download the onprogress event.loaded variable is set to twice as much bytes as there where total available.
I fixed the bug for me by simply dividing the result of getTotalRawBytesRead by 2.
This bug occurs since cordova 3.0.0 only on Android. Tests on iOS return the right result. I downloaded a video file from an apache http server.