Enter a unique number (&1) (view: &2)

What causes this issue?

You assigned the number &V1& twice.

System Response

The numbers for the distribution rules are used to uniquely name the
rules. This is not possible if you assign numbers twice.

How to fix this error?

Check the numbers for the distribution groups for view &V2&.
Enter unique numbers only.

Error message extract from SAP system. Copyright SAP SE.