It goes something like this. If you follow F/1.4's suggestion over mine, for the same scene, you will over-expose by one stop. Question is, is that a big deal? It isn't. The negative will be a little denser, but that can be compensated when prints are made. It simply isn't a big deal at all. I bet the images you are taking now are more than one stop off from optimum exposure. It's easy to do that and I do that all the time. I don't always take so much care in everything being optimum.
I said to use the box speed because that's what I do. F/1.4 said half the box speed because for most negative films, error on the side of over-exposure is safer than under. Basically, how big is a "pinch" of salt?