Diagnosis
You chose a field for a counter and determined that you wanted tooutputsubtotals for it at the control level given in the warning.However, it does not make sense to use this field at this controllevel, since, in the logical database, the control level field is at alower level in the hierarhcy than the field with the counter.

Procedure
Check whether your choice of fields, their sort sequence and the fieldsyou have chosen for counters make sense.