+1 what's already been said. "P" is the battlesight setting for 0-300 meters (may be marked something else, depending on what Slavic or otherwise language the builders spoke).
When I took Larry Vickers' AK class he suggested just setting the sight on the "1" setting -- then you're point of aim/impact is optimized for your most likely engagements at, say, 0-150 meters but will get you onto targets further out. Guys were making hits out to 225, 250 meters with that set up on iron sights during the class. (And guys were also doing the same with 25m zeros on various makes/models of AimPoint and some of the Russian optics.)