Rolls
Slam attack 1, damage (with advantage) - (1d20+7, 1d20+7, 2d8+4)
1d20+7 : (14) + 7 = 21
1d20+7 : (1) + 7 = 8
2d8+4 : (27) + 4 = 13
Slam attack 2, damage (with advantage) - (1d20+7, 1d20+7, 2d8+4)
1d20+7 : (7) + 7 = 14
1d20+7 : (18) + 7 = 25
2d8+4 : (41) + 4 = 9