When you benefit from the Frame bonus, you get to choose your bonus die. A d6 would be best if you're rolling a Cold action. A d10 is best if you're rolling a Hot action.
Due to word count I didn't have a chance to elaborate too much on that part of the rules, it's sort of a bare-bones sentence. The starting die roll for an action is your Pilot dice: 4d(6s/8s) + Frame bonus if applicable: 1d(6 or 10, your choice). Then after rolling those you may add more dice to the pool for Venting/Burning as needed.