So if you’re still in the playoffs or regular season, that means they haven’t officially announced what the cap for next season will be yet. The salary cap will be announced AFTER the playoffs end but BEFORE the draft and it will not change after that though. Once they show retirements, you will know exactly how much cap space you have for next season and it will probably be different than what it shows NOW.
I would always check how much space I had and who wanted what amount just before I started the draft because that is the last chance to make trades before resigning everybody.