More than 9 variables are used in the rollup

What causes this issue?

When a rollup is executed no more than 9 set or value variables can be
used at any one time. You are, however, using &v1& variables.

System Response

The surplus variables are not offered to be overwritten when the rollup
is executed. They will normally be occupied with their default value.

How to fix this error?

If necessary, limit the number of your variables to a maximum of 9.

Error message extract from SAP system. Copyright SAP SE.