Copilot Notebook Sees 78 Files but Only Accesses About 20. Why?

The notebook’s file count and Copilot’s answer about what it can see are different signals. Microsoft documents up to 300 grounding references for licensed Microsoft 365 Copilot Notebooks, while Copilot Chat notebooks have a 50-reference limit. Neither documents a general twenty-file limit.
First confirm the account’s exact notebook entitlement. Your Word, Excel, and PDF formats are supported, but a folder appearing in the interface does not establish that every file’s contents were used in a response. Copilot’s self-reported inventory is not a definitive diagnostic.
For a support case, select one allegedly inaccessible file that you can open directly, identify a distinctive passage, and record whether a targeted question retrieves that passage with a citation. Provide the notebook identifier, file count, permissions, client version, timestamps, and reproducible example privately.
This post cannot establish a Microsoft-confirmed cause. A service-side investigation is needed before blaming an undocumented regional or file-count restriction.