Hi, I know what you mean,
Repetier does take account of the offset (-23.7mm) in the printer settings against Extruder 2.
I think the problem comes because repetier doesn't correct the visible print area depending on which extruder is selected. As far as I know, the process of slicing uses the offset for absolute position but also doesn't take account of the printable area for each nozzle.
You have to avoid positioning to the left of the dot when using extruder 1 (also leave space for the brim). When using extruder 2, you have to use the opposite approach.
I guess, to avoid this you could specify the build volume parameters as only the green area, but as you can see, you can print bigger items than that limitation if using either single nozzle.