I just had the most ridiculous HOTK round last night. I had basically 3x-4x playfield running from the start all the way to the huge hurryup. I then hit the battering ram twice quickly, and literally screamed at what happened. The first hit scored my SJP with 3x playfield for 675m. Then the next hit scored the entire hurryup, probably now with 4x running, for 4.6 BILLION! That one shot was worth more than my highest ever score up to that point (3.8B)
So... I'm theorizing that your *multiplied* super jackpots add their entire value to the hurryup, which *itself* can be multiplied as well. Yow.
I didn't even make Iron Throne this game, but here's the aftermath. Got over 6B on HOTK alone.