Key figure scheme & lies within the reserved name range (7_ to 8_)

What causes this issue?

The first character of key figure scheme &V1& lies in the range
reserved for SAP.

System Response

You cannot edit a key figure scheme with this name.

How to fix this error?

Select a name which begins with A to Z, 0 to 6 or 9.
If you have already created a key figure scheme in the reserved name
range, copy it under a name which begins with A to Z, 0 to 6 or 9. You
can do this on the first screen of the transaction for maintaining key
figure schemes.
Then you need to adapt the reports and forms which use this key figure
scheme.

Error message extract from SAP system. Copyright SAP SE.