If I understand the question correctly, the flight spoilers(four on each side) are differentially operated by pairing two and two flight spoilers on each side with their respective hydraulic system, so to provide isolation and maintain symmetric operation in the event of failure of one system. The flight spoilers are used to increase drag and reduce lift, both in flight and on ground. They also augment roll by rising on the wing with up aileron, whenever control column input is 10 degrees or more. In addition you have ground spoilers(two on each side) operated by system A, so if you loose that one you'll only have half of the flight spoilers(two on each side, no ground spoilers) to spoil the lift at touch down.