Fria Ligans forum

I've noticed that when dealing with groups of advercaries, the game almost never tells you the number or gives any guidance on how big the group should be. I first noticed it with the nekatra in Ghazali and now I'm reading Emmisary Lost. In the first scene the PCs are confronted by a group of "fake guards". But how big is the group? One for each PC? More?
Also, the rule books says:

Groups of NPCs: When dealing with multiple NPCs, you can have them perform actions as a group instead of individually.

How does that work? Does the group have one statblock?