Hi Kumar,
The Sign varations differs depending on the Account Type & also depending on how you performed the Transaction DataLoad....
It is because in BW system the signs for this INC & EXP Accounts are reversed & when it displays in BPC System it will show in reverse sign..
For PL Account Hirearchy use INC Account type...
For clear understanding of this Signs kindly refer to this document link http://scn.sap.com/docs/DOC-26973
Aravind