This is a register form, it offers free account for the first 50 users, I wonder if it's good or common to put an account countdown for it.
According to me and based on the mistakes i have made in the past, putting any kind of condition for the user is not a good idea. Instead of showing countdown, you could tell them more about advantages of opening an account with your service. They should find value in opening an account at first place.
People would die to open an account only if you are offering them free money or huge discounts. Otherwise it does not make sense.