What do the lines on the back of Penn reels signify?

[fronty]

On the lower end of the spools, there are three lines/rings. I always try to spool up to the last line or a little above it, since it seems to be about 1/8" to the top. Do the other lines refer to how full the spool is (33 percent, etc.)?

[craww]

Its a reference to know how much line you have on your spool...Mainly for the saltwater guys that target long running fish that may spool you.