low bitrate in quicktime h264

hi,

trying to export a .mov with h264 codec with 30 000 kbps bitrate, but the highest result I get is about 20 000 (and for that I have to set 144 000 kbps in the bitrate settings). any idea why? is this normal or a bug in CC 2014.1? it doesn`t mater if I export from AME or directly from Premiere.

thanks for any help!

Windows 8

Nvidia Geforce 780

32 gb ram

Intel 3,5 ghz