Woo Hoo for baby fishies!! Is that not incredibly exciting??!! Congratulations!!
Do you have a male platy too? If so, and even if you don't, mark your calender today as the Bday and count out 28 days and mark that day. Moms carry sperm and can be pregnant for a few more cycles from one mating... And you can separate her on day 27 knowing that the drop of fry is anywhere from 28-32 days. If you mark it now and see her getting fat again you will know when to expect them. Good idea to keep a little pocket calender by the tank to keep track of all additions, water changes, new purchases etc. anyway. Make it so much easier to keep track.
Depending on the species they can often float around the first few hours (which makes them vulnerable to being snacks) and eventually drop down to the bottom to hide. Mollies and Swordtails will do this. My Sword had 7, then 11, then 65...
I had moved her to my 10 gal the night before, she dropped and I moved her back. Yes incredibly tiny!!
Now pristine water!!! will help them grow faster. If you had a fry tank, baby fish food, and daily water changes and the fry will grow way faster. Will you be selling these to your LFS? Or keeping them all? LOL Tanks multiply just like fish do you know!!