it depends on how many reads you get, but its a bit weird, the once in top 100 gets 1000 reads a day, at least, which keeps them up there ,
honestly you should not care about ranking unleash you are in top 100 and even then not really
I am in top 100 right now because I am on the weekly shelf, and I noticed your ranking goes up and down, I can be number 50, then return an hour later, and its 20, and then again later and its 70. and I have gotten like 6000 reads the last few days, the ranking system is so weird,