wamp800

Hi, I've bought an Wamp800. Now I have a question about the handling. I want to run it with 2 cabinets: 2x15" and 4x10". So I switched in stereo-mode with bi-amp-mode. Both cabinets are working. Now, what confuses me: I can switch from chanel 1 to 2 with the chanel-select. In both modes...