My browser and active.com don't like each other

I tried not putting a time and writing not applicable, it told me there was an error on the page and it would not let me submit it. I tried putting a true estimate, but it would not let me do that without providing a race name and official time. I was panicked about the race selling out so I quickly typed 3:20, which was above the proof of time threshold but allowed me to submit my registration.
I would hope to run faster than 3:20. But who knows? So far, as my run length has increased, my pace has stayed within 30 seconds of my short run pace, but I've only gotten to 6 miles. So I am comfortable saying I hope to keep my 10k under an hour, but I still don't feel comfortable actually predicting what will happen in the half. I used the calculator you suggested and got 2:12 as a prediction.
To be honest, I just want to finish without seeing the balloon lady and have fun along the way. I see getting a decent corral placement as a way to ensure I have time to enjoy the atmosphere of the race.