Basic Questions on Solar Install

I could use a little more clarification on the #8 wire size. I am using the Renogy wire size calculator https://www.renogy.com/calculators#tab_solar-cable and when I use it the recommended size is a #12 wire. This is for three 175W panels that have a optimum operating voltage of 20.3V each and optimum operating current of 8.62a each. It's my understanding if wiring in series the volts will be 61v for the three panels and current will be 8.62a. If I use 30' of length with a 2% drop it tells me #12 wire.