Not familiar with your screen cap app but usually when you end up with separate audio on separate tracks in an editing app you mix them in the editing app or export all audio tracks and mix them in Audition.
Stream 0 is video
Stream 1 is game
Stream 2 is voice
Stream 3 is PC
AE canot deal with multiple channels/ streams of audio in a file and that is that. At best it will use the first track in an untagged file, otherwise it should properly recognize the MPEG flags and use the "active" track from the file.
As Mylenium and Rick say, After Effects just uses one (the first) audio track from an input file. You are expected to do your mixing in an audio application, like Audition.