Controlling area &3, procedure &1: Sources of assignmts &2 and &4 overlap

What causes this issue?

You edited assignment &V2& and assignment &V4& of the allocation
structure &V1& in controlling area &V3&. The cost element groups or
intervals entered as sources in assignments &V2& and &V4& <ZH>overlap
</>. When a cost type is allocated to more than one allocation
assignment, the allocation structure is ambiguous.

System Response

You can still edit and save the allocation structure regardless of the
system messages. However, the intervals that overlap are liable to
either be ignored or cause errors during settlement.

How to fix this error?

Get rid of the overlap in the "source" screen by navigating in an
assignment and entering other cost element intervals or cost element
groups, or changing cost element intervals/groups that already exist.
In the "source" screen of an assignment you can display the intervals
of a cost element group by double-clicking on it. You can change the
interval assignment of the group via <ZH>Extras > Cost element group >
Change</>.
In the "source" screen of an assignment you can display your allocation
structure including cost element intervals/cost element groups by
choosing <ZH>Extras > Overview list
</>.

Error message extract from SAP system. Copyright SAP SE.