the 750 has an option called "shift to here" that allows you to move the guidance line to your current position.  It would eliminate a fair amount of button pressing and guess work in order to try and get the line matched up with where you actually should be. 

by using this, you could line the tractor up with the mark from the planter marker then hit "shift to here" and the line will match up with the mark (at least for a while on waas)