Your weekly appointment is at 10:00, but next week alone should start at 11:00. Editing the correct date is only the first check: Google Calendar also asks which events in the repeating series should receive the update.
Decide the scope before saving
In Google Calendar on a computer, open the intended occurrence and choose Edit. Check the calendar, date, time zone and your permission to change it. Make the small change, click Save, then read the choice of affected events. For a one-off exception, choose only that occurrence where this option is offered. A broader choice is appropriate only when the later schedule or whole series should change.
For a private example, use three Wednesday appointments at 10:00 on 4, 11 and 18 November. The intended result is 10:00, 11:00, 10:00. Do not use a shared production meeting merely to practise.
Check the neighbouring dates
Reopen the changed occurrence and the dates immediately before and after it. Verify their actual start and end times, rather than relying on the series title. If guests are involved, review who will be affected and the notification prompt before confirming. If the scope is unclear, cancel before committing and inspect the series first. This article did not edit a real calendar.