Freeing up space · Where your space went
Why did my free space go down right after a clean-up that worked?
Short answer: Your Mac makes backup references to what was moved or removed, so freed space can be held again straight away. It's not a failure: the space usually returns within a day, or you can release it now.
Because when something is moved or removed, your Mac makes a backup reference to what was there — so the space you just freed can be held again almost immediately, roughly in proportion to how much moved. It looks exactly like a failure and it isn't.
Storage Studio says so at the moment it happens, but only when it has actually measured that your Mac is holding a meaningful amount. The space comes back by itself, usually within a day, or you can ask for it now with Release that space or in Local Snapshots. Storage Studio also asks your Mac to release space right after a successful move. See what Release that space does.