Moving folders · Data Parking (the two-pane mover)
Why does Data Parking show a spinner instead of a folder's size?
Short answer: The folder is still being counted. Storage Studio measures quietly in the background so your own work comes first, and shows a spinner rather than 0 bytes so an unmeasured folder never looks empty. The footer says how many are still outstanding.
Because that folder is still being counted. Working out a real size means reading through everything inside it, so Storage Studio does it quietly in the background and always lets your own work go first. Sizes fill in from the top of the list.
The spinner is deliberate: an unmeasured folder never shows "0 bytes", so it can't be mistaken for an empty folder. The selection total in the footer adds up only folders that have finished and says how many are still outstanding, rather than quietly under-reporting.
Very large folders, or a slow drive, simply take longer. You can still move a folder before its size appears.