This is how I understand it, please correct me if I'm wrong in any fashion

Basically if it's 5 on 5 and each team gets called for one penalty a piece,
it'll then become 4 on 4 (exception being coincidental fighting majors).
Otherwise it'll stay the same situation. So if it's multiple penalties apiece,
even if they're equal on both teams (say 3 roughing calls per team), then it'll
stay 5 on 5. If one team is already shorthanded, then it'll remain 5v4 (or 5v3
or whatever).