You cannot change the target value of contract &1 from &2 to &3

What causes this issue?

If you make this change, the system will change the contract from a
value contract to a quantity contract.
The current contract is OTB-compulsory, which means that an internal
contract apportionment exists.
The internal contract apportionment for value contracts only contains
one value per period. This is because, for value contracts, all relevant
items are assigned to the same OTB buckets per period.
In the internal contract apportionment for quantity contracts, on the
other hand, different OTB buckets can be assigned to the contract per
period.
If a contract is changed from a value to a quantity contract, a data
inconsistency results between the contract type and the corresponding
internal apportionment. This will cause problems in subsequent
processing.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

System Response

How to fix this error?

Do not change the target value from a number greater than zero to zero
or from zero to a number greater than zero.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.