Amazon prime download size accuracy

Chromebooks can do android apps, which is how I run Amazon Prime video.  It allows several different quality settings:

130MB/hr is pretty danged good, and reported download sizes matched that estimate.  A couple of weeks ago the reported download sizes ballooned:

For those without a calculator handy, that is 249.8MB/hr, about double one would expect.  This got my attention.

I tried using an “ask every time” option (and thereafter picking Data Saver) and those estimates agreed with the 130MB/hr rate, in this case 50MB for a ~21 min show:

The displayed filesize for the download was 87MB:

I began to wonder if the app wasn’t misrepresenting the filesize.  I looked at the sdcard subdir where all the data is reportedly kept;  it had 319MB of data in it instead of the 499MB the app said:

319MB for 139 minutes (2.32hrs) of video = 137.5MB/hr, which is close enough to 130MB/hr.

Hypothesis  - Assuming downloads are being stored on the card where they should be, the Prime app appears to be misreporting the size of the downloads.

Test - I checked data usage for the app before and after another download.

•  predicted d/l size:  ~50MB

• reported d/l size in app:  `80MB

• data usage increase shown in android settings:  ~40MB

• android data folder showed 40MB increase in size

Conclusion - the app is showing the wrong download size, approx 2x as large as it really is.

WAG - this may have started when I went to the internal sdcard instead of a usb flash drive.  Don’t remember.