As far as I understand it, the more a member reads, the less you receive from that member when they read your story. If you think of it like the finite amount of subscription fees that it is, the money can only be spread so far. So, from what I can tell, it matters more WHICH MEMBER reads your stories, than how many members total do. There are medium articles written to clarify the formula, which are fairly interesting, but hard to actually attempt to draw a calculation from.