Quote from: Manual$game_variables[ID] = $game_map.battlers_group(GROUP).size
This sets the variable ID to the number of active Battlers in group GROUP.
For example lets say that Group 002 was my enemies group for alignments and I wanted to set variable 1 to the current size of that group.
$game_variables[1] = $game_map.battlers_group(2).size
Now lets say I also have group 3 as enemies and want to include them as well to the total.
$game_variables[1] += $game_map.battlers_group(3).size
Now Lets put that in event terms.

The $game_system should actually be $game_map ...
The second event page has SelfSwitch A on and teleports the player.
It is just an example of how I would do it. I don't actually use Blizz-Abs but that is what I got from the manual.