You don't need to think about how much storage space local snapshots are using, because they don't use space needed for tasks like downloading files, copying files, or installing new software.

Your Mac counts the space used by snapshots as available storage. Even so, Time Machine stores snapshots only on disks that have plenty of free space, and it automatically deletes snapshots as they age or as space is needed for other things.

If you want to delete local snapshots manually, turn off Time Machine temporarily: