Exclusion group & does not only contain group conditions

What causes this issue?

You are not just using group conditions with rounding settlement for an
exclusion procedure at header level.

System Response

In this exclusion procedure, only group conditions with rounding
difference settlement are considered. This settlement is active if you
are using group conditions without group key routines or group
conditions with group key routines and active rounding difference
settlement.

How to fix this error?

You should define the relevant exclusion group, so that it only
contains group conditions with rounding difference settlement.

Error message extract from SAP system. Copyright SAP SE.