As many times as the browser refresh button is pressed, form data will continually be sent. True the browser warns you about this but that doesn't solve the problem. The numbers are added to the previous numbers.
What is the best way to prevent a user from refreshing while they are still on the same form page? I put warnings of my own near the submit but... I'm not very confident in people even reading it.
"Your computer may catch fire if you hit your browser's refresh"