Terrapin laying eggs! Help!

So I adopted 2 terrapins 5 days ago. The female ‘Babs’ layed 2 eggs yesterday (1 crushed and 1 didn’t). I’ve checked her over and she feels like there’s another 4 eggs to be layed. I’ve set up a box with sand and put her into it to finish laying and nothing! How long should it take for her to lay the other eggs before I should start worrying? I’ve taken her out and put her back into water and given food and she looks like she is looking for a spot, but I am afraid the eggs are going to bind. It’s been about 36 hours since she layed the other 2. Any advise please?