Someone really knows what does channels do in h323?

In the h323 stack there is a parameter call max-channels. The default value is 6, but can go way way higher.
Testing with it, if I set this valeu too high, it breaks the SBC due to high memory reservation, and the SBC enter a boot loop. (I think a warning should be showed, because it crashes both SBC on the HA pair on activate). It occours at least on SBC version 9.0, 9.2 and 10, that I tested.
I understand the it sets the maximun channels per call. But whats a channel in h323? Whats used for? Why the default value is 6?

In the manual it says "Enter the maximum number of concurrent channels (or pathways used between nodes) allowed for each call associated with this H.323 stack". But I dont know how to find the value that i need to set here. It's like, one for audio, one for video, one for statistics…?