The target and reference period intervals must be the same

What causes this issue?

You have selected different period intervals for the target and
reference version.

System Response

The number of reference periods must be the same as the number of
target periods.

How can this happen?

You cannot copy the planned values of one period to several periods.

How to fix this error?

Correct your entry by entering the same number of periods for the
reference and target version.

Error message extract from SAP system. Copyright SAP SE.