I would have to ask how could you use it if it only came down to 15- It wont perform after 45 full stop. Probably set for 120 yards region like mine was, previous two owners couldnt use it and grabbed a bargain 10 years ago.
Set it so it tops out at 59 yards and play with rear focus (7 revs either untill goes out of focus split the difference), job done. May come down to 10 then and count the yardage up to that, easy. Still get a shot off on sub 8 yarders!