SAP Message VAL603 - The existing book values have different signs

Diagnosis
You want to run a manual valuation for the position as at &V1&. This isonly possible if book values for the position are available in thesystem for date &V1&.
The book values entered for this position have different +/- signs. Asa result, the system is unable to perform the valuation consistently.

System Response
Valuation is terminated.

Procedure
Enter consistent book values.