Funny thing is... That % doesn't even do anything. Its just a reference point (A bad one at that.)
EXP is team attack based in Shared EXP rooms. Higher your team attack and personal attack are, the higher your exp is. Aka, if you don't sink anyone until the last minute and just keep damaging and repairing and both teams got into the 900k team attack range and your personal was 150k you'd get 80k exp
Where as if you only had 600k team attack, a mere 54ish k