Tuhi, your storage assistant · What Tuhi knows
Why does Tuhi sometimes say "I don't know"?
Short answer: Tuhi would rather say "I don't know" than guess. Each answer about your Mac is checked sentence by sentence against what Storage Studio really knows, and anything unsupported is left out. She runs only on Apple Intelligence on your Mac.
Because a plain "I don't know" is better than a confident wrong answer. Every answer about your Mac is checked, sentence by sentence, against what Storage Studio really knows, and anything it can't back up is left out. When nothing is left, Tuhi says so.
Tuhi runs only on the Apple Intelligence model on your Mac — no online model is used, so your questions and files stay on your device. That model is small and fast, which is another reason the checks matter.
If she doesn't know, try asking more specifically ("how much space do my backups use?"), or open the screen she points you to. For questions about the app itself, the user manual has the full detail. See whether Tuhi uses your real numbers.