Use the left or right side of 1,3,5 or 7 to record a mono track. The input options should show something like
1 - Left1 - Right1 - Stereo 1 - Left is channel 1 on the interface
1 - Right is channel 2 on the interface
1 - Stereo are channels 1 and 2 on the interface
3 - Left is channel 3 on the interface
3 - Right is channel 4 on the interface
and so on