The SEC is worded in such a way that other teams can use the card you chose, this is not intended, correct?
Can you upgrade the card you choose?
The example makes EC even more confusing. Maybe a better example with detailed pick(s) a team (has to) make and the result of it?
Choose player and a value of +1 or -1
4 teams pick +1, 2 teams pick -1
4*1+2*(-1)= +2
In their battle, ONLY THEY get a modifier of +2. So if they win they get +2 salvage, if they lose they get +2 Discard. This does not effect the opponent.