The event count in the upper right of the issue is showing a number that is higher than the number I see when I click on the All Events tab.

The number in the upper right corner is the total number of events grouped into that issue for the entire issue's lifetime.

The number in All Events is showing the total number of events that are currently accessible. They can be different due to Sentry's 90 day event retention window. After 90 days the event is deleted from our servers and no longer visible in Sentry.

Note: free Developer plans have a 30 days retention period.