Using Media foundation , a 1 minute HD (1920*1080) clip is estimated at 44.9 MB for HIGH - actual size is 318 MB
Using FFMPEG same clip, estimated at 18.7 MB for LOW - actual size is... 176 MB. For MEDIUM, estimated was 44.9 and actual was 212 MB
This is a known issue, it's pretty much impossible to get the size exactly right. There are a few things we can do to make it closer, but this hasn't made the cut yet for a release.
I apologize for the trouble, but we have to pick and choose where we put our time and resources, and this seems like a bug most people can live with. If we get lots of feedback to the contrary, we will re-adjust.
