Several different measurements can appear during cleanup, and they are not expected to match in every case.
Scan estimate
The scan counts supported accessible candidates at a point in time. Files can change after scanning, and inaccessible locations are omitted.
Selected size
This total reflects the items currently selected. Shared storage, links, sparse files, packages, or duplicate references can make logical sizes differ from physical disk use.
Removed size
Items can be skipped because they changed, are in use, require permission, or were already removed. Review the completion result rather than assuming the selected total was removed.
Available storage
macOS manages purgeable space, snapshots, caches, and file-system allocation. Finder or System Settings can update later and may categorize storage differently.
An application can also recreate cache immediately after cleanup.
Verify the outcome
Run a new scan, wait for macOS storage reporting to refresh, and compare the same volume and unit. Do not repeat removal solely because two displays use different totals.