I had a problem rendering an MP4 from a rather complex 5 minute MEP 2014 video. After some fiddling around I decided as a next step to split the project roughly into two and see if I could successfully export them separately. But I accidentally ran both with Export selected range only switched off. So I got what should have been two identical full length videos. (Both were now OK.)

Yet their file sizes are significantly different, at 281 MB and 298 MB respectively. The variable bitrates reported by MediaInfo differed by roughly the same 6% variation, at 10.2 and 10.8 Mbps respectively, which would account for the file size difference. (I can't edit the subject!)

But I'm puzzled why the bit rates would differ on two successive exports of exactly the same project?

It's also odd that GSpot reports slightly differently to MediaInfo on bitrates:

File #1: MediaInfo 10.2 Mbps, GSpot 10.061 Mbps (which rounds to 10.1)

File #2: MediaInfo 10.8 Mbps, GSpot 10.669 Mbps (which rounds to 10.7)

Incidentally, MediaInfo gets the seegar for correct rounded file size of 312,388,566 byte file #2 at 298 MB, versus 297 MB from GSpot. Presumably a coding error in GSpot's rounding.