Periods have been summarized

What causes this issue?

For one block, several periods are available that overlap so that they
cover an entire block period. The system has summarized these block
periods into one block period.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.