This was my first kickstarter to support. I just want to confirm I have everything set up right and one question. So I confirm my address, phone and reward selection in pledge manager and I'm done? I was curious, if I come back later and add something...does KS go through the whole refund entire amount and charge me for the new amount or will it just bill me for the difference? I wanted to check in case my credit card processes the charge before a potential refund (which is has done that before).