Don't worry about the numbers, we don't even know if they're talking about wet or dry basis in the video.
Battenkiller used to post a lot on moisture content, here is one of his posts on the subject that talks about the two. 25%-19% on the meter should put you in a good spot according to BK.
"There are different ways of expressing moisture content, which don’t at all have to do with the method of determining them. The EPA test loads are Douglas fir that is between 16 and 20% wet-basis. That is expressed by taking the weight of the water present and dividing it by the weight of the entire split. Your moisture meter is calibrated for Doug fir as well, but the calculations done by the chip inside of it (or the width of the scale divisions if you are using an analog meter) are done using the dry-basis method of expressing moisture content. That is expressed by taking the weight of the water and dividing it by the weight of the dry fiber that would be present in the wood after all the water has been theoretically driven out (as would be done in a 215º oven in a lab).
Naturally, you get very different numbers, and this effect grows increasing more substantial as MC rises. It’s a mathematical thing, and has nothing to do with the actual wood, which always has the same amount of water in it.
If you want a real easy way to convert dry-basis meter readings to the wet-basis used by the EPA tests, just divide the number on the meter by that same number plus 100, and you will get the correct wet-basis MC every time.
For example, the meter says the wood is 25% MC. Add 100 to 25, then divide that number (125) by the original reading. 25/125 = 20% MC wet-basis. The high end of the EPA test range… perfect for you stove.
In another case, the meter says the wood is 19% MC. Add 100 to 19, then divide that number (119) by the original reading. 19/119 = 16% MC wet-basis. The low end of the EPA test range… perfect for your stove.
As far as a definite cutoff number, I don’t believe it exists. The way you load the stove, the type of wood, the way the wood is split, the amount of coals in there, the internal stove temps, the timing and size of wood additions, the strength of your draft…. all things that can and sometimes do have a more profound effect on the burn then just MC and draft opening. For me, the theoretical cutoff is 25% MC wet-basis (33% MC on the meter). That’s 5% more water in the wood than the maximum allowable MC in the EPA test loads. Above that, you will likely have a progressively harder time burning your wood without micro-managing the stove."
