SAP Message TU381 - Period length for alt. portion &1(&2) differs from orig. portion &3(&4)

Diagnosis
You entered alternative portion &v1&, which has a period length of &v2&.
The meter reading in the installation refers to portion &v3&, which hasa period length of &v4&.

Procedure
Select an alternative portion that also has a period length of &v4&.