A grouped datasheet can look like a small table of ordinary cells. Its total, however, may represent many underlying records. Typing a preferred number over that total would not tell Access which source observation should change.

Identify the query and the particular field that resists editing. Keep a copy of the database before changing records. Distinguish a data correction from a request to alter the report's calculation rule; those changes require different evidence.

Inspect how the result was constructed

Microsoft lists queries containing GROUP BY and crosstab queries among those whose results cannot be edited directly. A calculated field also cannot be edited as an ordinary stored value. The query's design can therefore explain the behaviour without any fault in the keyboard or a missing permission.

Open the query's Design or SQL view and identify its source, grouping fields and aggregate. For a fictional category total of 13, the source might contain quantities 6 and 7. Decide whether one of those values is wrong, whether a record should be excluded, or whether 13 is correct for the current rule.

Find the specific observation to correct

Use a separate select query or the database's normal record-editing form to inspect the contributing records with their identifiers visible. Follow the approved editing route for the database rather than turning the summary into a different query just to make cells accept typing.

If the second observation should be 8, confirm that against its source evidence before updating that record. The expected category total would then be 14. If the issue is that the second observation belongs to another category, changing its quantity would be the wrong repair.

Reopen or refresh the summary through the application's normal workflow and verify the affected group. Check an unchanged group as well so the correction has a clear boundary.

If the query has no aggregation, investigate other editability causes separately, including its joins and permissions. Do not apply this explanation to every read-only result. Keep a record of the source correction and its expected effect so another user can distinguish a repaired observation from a manually adjusted report.

Sources: Microsoft: editing Access query data.