So yeah, I kind of just noticed that a couple days ago, I've been trying to figure out what this "Team Bonus" means. (shows up when you press Start during a match)
And this number somehow adds to the total favor so It seems like a somewhat important thing to know.
The more people on your team and the more kills/favor/objectives adds to your Team Bonus.
I played a game where I was on a team of 3 against a team of 4, they had a crappy score across the board and they received over 5400+ points as their team bonus simply because there were four of them and my team lost the game even though we had more kills, favor, and objective. I had more points than all the remaining players and we still lost because of the opponents' Team Bonus.
team bonus come from holding altars I reckon
Since the points from altars taken over time can't be given to everybody (or any single person), they put it under "Team Bonus"
Points that come from holding the altars overtime (not the initial capture) go into the team bonus category. Team bonus has nothing to do with how many players are on your team.