Welcome to the suck.
At a guess, you’re a mid-seniority OF3 and/or PAS on the same kind of pay, who has AFPS 75 rights, and has just hit their 16 year point?
If you go the annual allowance calculator, use the figures provided in conjunction with this genuinely good handout
https://assets.publishing.service.go..._MASTER-OS.pdf
you’ll have all the answers you need.
I suspect (based on personal experience) that your unused AA from the last three years will see you safe.