Well, as far as I know, health is the number of resources, which is estimated to be the number of downloads counted by Thunder. The denominator seems to represent the total number of downloads, and the numerator seems to be the effective number of downloads. Facts show that the greater the number of resources (numerator and denominator), the greater the success rate of downloading. LZ, when you say that you can download if your health is 0, you mean that sometimes you can download even if the number of resources is 0 (but it's not very fast. If you look at the download details, you will find that there are not many downloads, so other users may give up halfway. Generally speaking, health status can only be used as a reference. Of course, you can compare the quality of each seed.
The above is my personal opinion, I hope it will help you.