SAP Message 6D720 - The "valid from" date must be within &1 and &2

Diagnosis
Each sales grading is assigned a valid-from date.
For limited agreements this date must lie within the period between theagreement start or date of the first posting and the agreement end.

System Response
The system expects an appropriate entry.

Procedure
Enter a valid-from date which lies between agreement start or date ofthe first posting and agreement end.