Apps · Moving apps to your fast drive
How much space does moving an app free up?
Short answer: About the app's own size, shown on its row. Its settings and data stay on your Mac; Offload frees those too.
Roughly the app's own size, shown on its row in the Internal tab. The app's settings and data stay on your Mac, so they aren't counted.
To free the app and its data, use Offload instead. And if your free space doesn't seem to update straight away, macOS may still be holding the old copy in a local snapshot for a while — see snapshots and freed space.