Hi,
That is due to the number of records your select for display in RSA3. Keyfigure values normally get summed up for same Key fields in the Function Module. Thats why you see the Difference in the Key figures.
If you still want to validate the records, pick same no of records in PSA and RSA3 for the same kry fields and validate the key figures.
Regards,
Poomagal S.