I have to pay an estimated $129 in taxes, and made a $50 payment direct to the IRS for my extension, can I make a second payment the same day? What if I am owed a refund?

I paid $50 earlier today to get an automatic extension to the IRS, I believe we have a refund coming, but am missing a W2, and just want to be safe. TurboTax estimates $129 owed basing info off our last pay stub, so can I make a second $80 payment to be on the safe side? If it turns out we do not owe, will I get a check for the refund?