The Match Renumber Wizard is accessed through the By Shooter Number tab on the match registration screen.

 

 

If the match is squadded, you can select to have shooters renumbered by squad.

Within each squad, they can be numbered alphabetically or by IDPA number.

As shown below, if any shooters do not have valid IDPA numbers, that option is not available.

If you have one large squad (for your SOs shooting the day prior to the match, for example), be sure that squad is number 90 or higher.  Otherwise, the chunk of numbers allocated to each squad may grow much larger than needed.