The game does it to young players, to simulate how hard and unpredictable it is to assume how good they will become. So essentially in any new game started, the game will give these negative PA guys a random Potential ability in the range chosen.
SO, for example, Say a player has a -9 PA. That means whenever a new save starts, he'll be given a random PA between 150-180, because the -9 range is 150-180.
The -10 range is 170-200, the -95 is 160-190, -9 range is 150-180, the -85 range is 140-170, and so on.