&1: exception aggregation ref. characteristic has incorrect data type

What causes this issue?

The formula "&V1&" with the exception aggregation "&V2& [&V3&]" has the
exception aggregation reference characteristic "&V4&".
For the exception aggregation "&V2& [&V3&]" only reference
characteristic of the following data types are allowed:
+,,NUMC - Character string with only digits
+,,DATS - Date field (YYYYMMDD) stored as char(8)
+,,TIMS - time field (hhmmss), stored as char(6)
The exception aggregation reference characteristic "&V4&" has a
different data type.

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.