As many as you want. In fact, you can make just one, although I don't know why you would bother - you can always refrigerate them for later, or up to a few dozen. You can fill the Instant Pot right up, placing the eggs on top of each other in several layers, and the cooking time will still be 5 minutes. The Instant Pot will take a little bit longer to come to pressure, but once it does, the eggs still need the same amount of time to cook.