User &1 is not the default user &2 for task category &3 in Customizing

What causes this issue?

In the Customizing activity <LS>Specify Task Categories and Tasks</>,
the default user &V2& has been specified for tasks of the task category
&V3&. The current user &V1& does not match the specified default user
&V2&.

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?

Assign the task to the user &V2&. However, if you want to allow another
processor for the task, you can keep the current user.

Error message extract from SAP system. Copyright SAP SE.