If the dial is painted in EV, you make a subtraction.
If the dial is painted in foot-candles, you make a division and then extract the base-2 logarithm.
The result is the same, but one of the two cases is more immediate
Adams should have bought a light meter with the proper dial or have it rewritten with the "proper" scale.
EDIT: I read now on Wikipedia the EV concept (I would say convention) was developed in the '50 in Germany. That would mean that before that epoch light meters did not indicate EVs. I find EV the best invention since the iron thread to cut eggs. I memorize and read on the instruments EV15, EV12 that's much easier to remember. EV 12.3 is easier to memorize than 1/125@f/5.6 + 0.3 stop.