That is essentially correct. These are configured as stereo-pair line inputs. They are mostly used for inputting stereo, line level signals like a keyboard or a CD player.
You could input different signals on the pair (e.g 5/6) but, since they are stereo, you only have one gain control for the pair (e.g 5/6) and a balance control instead of a pan. The balance controls the relative gain of the L/R signals as opposed to moving the signal left and right.
You can use the left inputs (5 and 7) as mono inputs.
