One of the easiest ways to know, is to measure how much line is reeled in with ONE complete turn of the handle. Have someone assist you in pulling out exactly 10 feet of line. Give the handle one turn and then measure to see how much line was reduced. This will give you a quick way of knowing what each turn will do to your depth. Now each turn won't be exactly the same as the circumference of the spool is slightly different with line let out or taken in, but it will give you a very accurate estimation.
If you are fishing 25 feet deep and want to raise to 15 feet and each complete turn raises it 24 inches/2 feet (example) then 5 turns of the handle would raise the lure 10 feet you are right where you want to be.
Capt. Craig Copeland
2013 Nautic Star 2110 Shallow Bay Boat
Humminbird HELIX 12 CHIRP MEGA SI GPS G2N
Nautic Star Boats Pro Staff (nauticstarboats.com)
Redneck Fish'n Jigs Pro Staff (redneckfishn.com)