Treating for Varroa when none is present 1) is costly and 2) creates a less effective treatment if/when Varroa infests the hive.
I have in every hive varroa. I do not care to calculate them. It helps nothing.
None is present. Somebody lives so far that varroa have not arrived. But when it arrive, it will not vanish.
I put in every hive oxalic acid liquid. It takes 20 seconds at autumn. If I calculate, it surely takes many minutes.
I do not understand those calculations at all. If someone want to find varroa resistan hives, then is necessary.