Does 12.5V remaining mean I only used 10% of charge?

[wasabi]

Barnacle Bill posted this chart awhile back on a prior battery question I posted. Today I fished for 5 hours using my 40-lb thrust motor, spending about half of that trolling on low and the other half using the trolling motor to make a lot of small changes to boat position. In addition I probably used the trolling motor on medium for about 1 mile getting to/from my fishing grounds.

I expected the trolling motor to be more depleted at the end of the trip, but I checked it with a voltmeter a half hour after leaving the water and the steady state voltage was 12.5v. Does that mean I really only used 10% of the charge? The battery had a full charge before leaving. I charge it when I get home, then give it a top-off or trickle charge if it has been more than a few days.