Dear Ragavendra,
Please do cross check your outbound document, either there is any WBS appearing in TAB (Financial Processing). Normally it would not called at automatically although you are using the movt type 601 Q, you have to give it manual. I have check this, when i give WBS in tab Financial processing, system is reducing the stock.
For this you can see the attached screen shot.
Kind Regards
Mohsin Abbasi