If you are younger than 65 and you leave PSPP before you have two years of pensionable service (including CPS or service you've purchased or transferred in), you will not be eligible to collect a pension at retirement. This is what the term "not vested" means.
If you leave the Plan, PSPP will send a Termination Statement with your options to the address we have on file. You will have 90 days to make a decision and let PSPP know; if you do not, your share of contributions with interest will be paid to you with income taxes withheld.
If you need help understanding your Termination Statement you can book a one-on-one session.