This is probably hidden in discussions somewhere in the forums but I couldn’t find it.
During the hot discount times its hard to game more than a handful of dinos hatched to take advantage of the discount, at least not without depleting your dino bucks.
I found that a good tip for increasing the number of dinos you get the DNA discount on is by filling out at least he first slot in your hatchery then attempting to hatch a dino and cancelling when you get asked to pay dino bucks to open the next hatching pod. If you have them all full, you just get asked to manage your hatchery, but it also works.
This will “purchase” the dino for the discounted DNA amount and leave it in your market. You can then hatch it at your leisure.
This trick will only allow you to purchase one dino of each type but usually that will save you a bit of extra DNA if you select a few dinos. Conveniently, hybrid dinos take much less to hatch but are expensive on DNA so these are the best ones to choose to take advantage and not clog up your market.