Hi... well the snails carry eggs that are fertilised and are laid they hatch within the day depending on the snails breed.
She could of been full of eggs when you got her.
If I'm right, I'm think that the snail you are talking about don't have that many offspring anyway.
And you can always sell the ones that you don't want to keep instead of letting other snails feast on them
Oh wow, you're so lucky! I've had my Sulawesi snail for about 6 or 7 months and not a single baby. You got 4 in one go, that is pretty rare from what I've learned about them.
Depending on their tank mates I think it is safe to leave them in the tank. Just make sure they are getting enough food. They are omnivores, so they do need some meat-based foods as well, not just plants/algae/veggies!