Well I fourth that papapascucci with the add detail.....
dC0610 (IOP)
Image On Paper: Registration Setup is used to adjust the image squareness, magnification (IB-to-OB and LE-to-TE), registration (IB-to-OB and LE-to-TE), and paper skew for both simplex and duplex printing.
If your adjusting this you probably have something else going on like bad Registration Steering Drive Rolls.
dc0610 (IOI)
Image On Image: Used to adjust the absolute cyan position and IOI registration for each primary color. This ensures that the composite of these colors meets established Image Quality specifications for image registration.
Before you run dc0610(IOI) perform ADJ 6.2.
The purpose of this adjustment is to set the MOB LED current so that the MOB Sensor accurately detects the IOI Registration Marks On the Belt.
I've only had to run IOI after ROS replacement, but it won't hurt to run it every 6 months to a year.