Hi, beginner's question here. I'm looking at 2 ampacity charts for 12 AWG cable. The first one puts it at 20 amps, which is what I had always thought it was. The second chart has variable ampacity depending on if the cable is rated for 75 C or 90 C. For instance, AWG 12 is rated at 32A at a temperature rating of 75 C and 35A at 90 C. Is the second table referencing higher grade cable than the first or something? Can anyone explain this to me? Thanks!