Freeing up space · Where your space went
Why does the space breakdown say the answer for a period is incomplete?
Short answer: The period reaches back before something was being measured — often held backup space in older readings — so Storage Studio flags it rather than present a partial answer as complete. It improves as newer readings accumulate.
Because the period reaches back before Storage Studio started measuring something, so part of the picture isn't available for it. Rather than pass off a partial answer as the whole story, it says so at the top.
The most common case is long periods — weeks rather than a day — where older readings didn't record space held by your Mac's automatic backups, so that can't be separated from the rest. This improves by itself as newer readings replace the old ones. Shorter, recent periods give the fullest answer. See the unaccounted-for line.