~FYI~ the higher township #s (e.g. 21) are in the northern tier of the county; the lower range (e.g. 6) is the western part; viz: from south to north, the townships go 16-21; from west to east, the ranges are 6-10;
Look at the (not-perfect-scale) Perry Co. Township and Ranges map to find each township-range.
There is a very good explanation of the township-range system to be had at Land use self-taught sponsored by the Int'l. Internet Gen. Soc. University, which explains this in Lessons 2 and 3.