I have no experience with the tanks on a 182 but in most aircraft an accurately calibrated dipstick is the only way to know what quantity of fuel is actually in the tanks. If you are not sure it is well worth the time to drain the tanks and calibrate the dipstick and if possible the gauges. I have found considerable difference between aircraft of a similar type and some dipsticks can be way out and are more of a hazard than an asset. I mentioned in another thread recently that most incidents revolve around fuel / firewall forward so knowing rather than guessing how much fuel is available is vital to fight safety.
Rod1
PS this is a general comment and not aimed at you ExSp33db1rd.