Impedance - Real World Limits?

I ended up buying an Ideal 61-164 circuit tester. It was more than I wanted to spend but it found a bootleg ground with little effort (since remedied).

But you know how it is, to a man with a hammer the world is a nail. I've been doing all the tests. I have a 20 amp/12 gauge circuit that is showing a .33 ohm hot impedance (limit is supposedly .25). I am going to do the best job I can on this place. The other instances I've found turned out to be old wire nuts that weren't making a good connection. I haven't torn into the wall but this wire appears to run directly from the panel to the outlet I'm testing. I temporarily ran a piece of 12 ga. wire from the panel to where the outlet is, 38-40 feet. It still reads .30 ohms of impedance on the hot. Where am I thinking wrong here? Is that too long of a run (doesn't seem plausible) or is .25 ohms impedance on the hot not a serious limit? How much is too much.

I'm also not sure how seriously to take the values shown on the tester. With my test setup I show .30 ohms impedance on the hot but only .08 on the neutral. Seems like they would be the same if everything was working...