If you are only talking about say 1/2" difference ... on the non driven slide arm there are two bolts on top of a plate. The holes are slotted. Loosen the two bolts and shove the slide in or out as needed. Retighten the bolts. Don't loosen the 2 bolts on the plate with the pusher bolt ... these adjust tilt. Do not do any adjustment that requires jumping teeth on a gear rack as the change will be way too much for what you describe.
Look on page 16
https://www.lci1.com/assets/content/...g-gear-web.pdf