Declination is easy with these if you realise the following; Some of the original home installed satellite dishes didn't even have declination adjustments. When they quickly realised they needed it, they modified the polar mount brackets by drilling the 3 fixed holes in-line on the top bracket. That allows 3 FIXED settings to get some declination, or down-tilt of the dish. Back when there were only maybe 6 sats or so total (and analog transmission, which isn't as critical as digital) in CONUS orbit, it didn't make much difference, as declination didn't need to be all that close.
So, unless you modify the bracket with some all-thread in place of the 3 holes, just put the bolt through the hole that approximates the amount of declination needed for your location. If that dish was originally located within 25 miles of your house, and set correctly, just leave the ideclination setting were it is now.