Abbreviation & is reserved for indicating time substitutions

What causes this issue?

The shift abbreviation &V1& is reserved for indicating time
substitutions in the target plan or actual plan in Shift Planning.

System Response

You cannot use the shift abbreviation &V1& here. Choose another
abbreviation.

How to fix this error?

You can either use a different shift abbreviation, or you can choose a
different abbreviation for indicating time substitutions. You can
determine the latter under 'Default values' --> 'Define shift
abbreviations for special functions'.

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.