Bit, unless you are doing some audio recording (which I think you aren't) you won't really need multiple busees, so I'd leave that at 0. Multiple busses are useful to "group" the signal coming from multiple tracks, for example a drum. You can route each individual part of the drum to a single bus and control the whole volume of the drum using the bus while still being able to tweak each part independantely at the track level.
For basic video projects I doubt you need this.