Stock adjustment

Hello ,

Kindly help me with the following situation.

Our client has a legacy and SAP system in place (purchasing and accounting )as well as BW which is used to find any insync issues between the two systems and correct as required.

The situation is :

For a plant the stock in the legacy system is 1000 and same in SAP(but 800 in plant stock and 200 in consignment stock). the BW does not show any diff as total stock is same.

How can I increase the plant stock by transferring it from consignment stock?

Also how plant staock can be reduced(opp case to above)?

Regards,