Congrats! I thought I was doing well to get 48 subs this month! Hope you're enjoying your success so far.
As for visibility and that lot. Basically from what I've gathered, the more you upload the more your novel gets seen and therefore, potentially, the more you grow.
As for Tapas and how they handle promotion, well, it's kind of unknown or at least not strictly explained. Getting noticed can defo be partly luck! Good luck, hope your growth continues.