He does 1d8+1d6+17 per attack. So he did 100 or so in round one of her 180 points.
Celtavian has set out the damage. I assume that is 1d8 from weapon, +1d6 from Hunter's Mark, +2 from magic, +5 from stat, +10 from feat.4 bow attacks (assuming ranger plus sharpshooter plus Dex 20 plus +2 bow) is 5d8+68 damage. Not bad rolling on that 5d8.
Even with the resource expenditure and house rule that lets the PCs double down on buffs that's some good luck for the PC.
The average of 1d8+1d6 is 8; so the average overall is 25 per hit. Four times 25 equals 100.
I'm not going to do the maths on rolling 4d8 + 4d6, but I think the likelihood of that tending towards average is going to be pretty good.
Based on the parameters that [MENTION=5834]Celtavian[/MENTION] has provided, I don't think this is particularly lucky. A fairly average number of hits (.775*5 = 3.875, which is not much lower than 4) for an average amount of damage.