Realistic Pro-2001 Freq search function

I just got ahold of a great, old, Realistic Pro-2001. 16 channels of LED bliss. Although #16 seems to be either shot out or reserved for something. Programmed it easy enough with a Radio Shark search. Has neat FS & SS buttons that seem to stand for Fast Search & Slow Search. It has a frequency search feature but I cannot seem to figure out how to program the ' up ' & ' lo ' of the search parameters. Rat Shack doesn't have any info on it & searching online proved fruitless! No one here seems to have asked either...