Usually 64 players start tourney. If you are exempt, you are automatically one of the 64. Take the number of players exempt and subtract from 64, that's the number of spots open to pba members that have to qualify! If there were 12 open spots the top 12 qualifiers would enter the tourney.
A two year exemption means a bowler has the option to sit out for two consecutive seasons with pay! Once the two seasons have pasted he would have to return full-time to bowl on a regular basis.