You cannot create an additional line with &1 initial 0 or BLANK

What causes this issue?

When adding additional lines, the system finds that target field &V1&
has a value of BLANK or "zero". This is not permitted.

System Response

The error is displayed in the application log.

How to fix this error?

Please change your derivation strategy for the target field &V1& in the
Customizing activity <DS:SIMG._ISPSFM_N_FMCUDERIVA>Define Derivation
Strategy for Additional Budget Line Items</>.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.