Diagnosis
A specific namespace is reserved for custom settings for currencytranslation (translation key, translation timeframe, translationprocedure, exchange rate period used, and procedure for exchange ratedetermination). The settings delivered by SAP start with a numeric digit
, whereas customer settings start with an alphabetic character (letter).
The value you selected (&V1&) is not in the customer namespace.

System Response
The setting &V1& cannot be created, changed, or deleted.

Procedure
Either call up input help and select an existing setting, or create anew value in the customer namespace.