Everwing Facebook Messenger Hack

I get to the step where you change values and it won't let me type anything in there. Why is that?

Edit: I'm on Chrome as well. I open in a new tab and I can't find it where it lets you change value or anything.

Doesnt work.
Chrome now displays {"message": "Invalid argument: coin", "error": true}

Its because of numbers like 31456.123533 it must be 31456 change this and it will work