Full context: though some of the milestones nominaly "unlock" stuff, none of them really "do" anything in practice.
100 technically unlocks adshare. You won't be getting any money from it until something like over 1k subs and a ton of regular readers and posting. Most people are counting their adrev in cents years after unlocking the 100sub mark.
Same for 250, technically it unlocks ink donos, but unless you already have a really invested fanbase or even a few really invested people who have already said "I want to pay you for this", then no, you're not getting any ink donos. You might get some for inksgiving, but historically you don't need 250 subs to unlock that if you do the admin.
You also can't withdraw money from your tapas account until you have over $25 in there so there's a snowball's chance in hell you'll get any actual effect from the milestones as they happen.