The principle is that the two columns are two separate redundancy combinations which are internally interconnected by L-Band switches. So each column itself will provide redundancy, where in slot 3 and 8 the redundant modules will be plugged. So per 19" chassis with its maximum of 10 modules you can realize two independent redundancy configurations.
There is a second redundancy definition (intern2). If you select this redundancy definition, the left and the right redundancy combinations will be switched synchronous. For example if in the left column slot 2 is switched to slot 3, then in the right column slot 7 is switched to slot 8.