What does TiVo mean by "GB" on the Program Detail dialog?

Assuming it calculates the GB the same on the S3 and the S2, using the data returned in the XML data when connecting to my S2, I picked a program that reports its size as 2.14 GB on the TiVo. The XML data said the size is 2303721472. Dividing by (1024)^3 gives about 2.1455. Testing a 2233466880 XML reported size (2.08 GB) and the TiVo reports 2.08 GB.

So it looks like it does using the standard definition of a GB, but truncates anything after the 2nd decimal point.

Getting TiVoToGo today let me transfer a file onto my PC that was marked 7.46GB on its Program Details dialog in TiVo (last week's episode of Heroes). On disk, the .tivo file was 7,382,529,547 bytes long, about .1% less than 7.46 billion. So, S3 would seem to be reporting file sizes in 10^9 byte units and not 2^30 (and for some reason, content takes slightly more space on TiVo than it does when transferred off).