Yes it's done on mega bytes not bits, so 10MB would be 10,240KB.
However, there will be some variation. This is because when you upload the game, it doesn't count ALL the music and sounds as they are dual encoded to AAC/OGG, it will only count one set of audio files.
This means that if your game is over 10MB it might still be allowed through if discounting one set of audio brings it to <= 10MB.
It will count the .ogg files but not .m4a. We quote 10MB to be safe, if your game is <=10MB it's guaranteed to get through. If it's more, it might not, but this is up to you if you want to exploit it.Tom2012-02-01 17:13:24