When using the SU-800 you can set that switch to either Commander position or Commander Closeup (Macro) position. Leaving it set at the Commander position is where some users leave it set at. That setting will serve you well for macro also.
Perhaps the big difference in switch positions is that when set to Commander position, your power adjustment to the remote flash units is made in Exposures Values (E.V.) such as +1.0 EV, +.7 EV, -.3EV etc.
When you change the switch position over to Commander Closeup you will notice that now the light (power) adjustment of the remote flashes is made in lighting ratios, rather than in EV values.
So a ratio of 1:2 tells you that the left side of the subject is receiving only half the light as that on the right side. 1:1 is equal light on both sides etc. Sometimes we find it easier to adjust the flash output working in terms of ratios rather than EV values. I certainly do at any rate!
So if I am going to shoot a flower close up...... I switch to Commander Closeup position and adjust the flash power (of each lens mounted SB-R200 flash units) using ratios rather than EV. Be it 1:1 or whatever ratio I feel I need to use to get the result I am looking for. For all other photos I just keep the switch set to Commander position. Perry