Minus 11 was not your SCORE. You were 11 strokes under par. Par can be 70, 71, or 72 - depending which course you play.
At -11 on a course having par of 72, your SCORE would be 61. On a par 70 course your SCORE would be 59.
A score of 59 won't lower your score average if your score average is 59.79.