Oh man my math was off then. This is what I got

85 points x 80 frags = 6,800 points for nagato
150 free pts x 7 days = 1,050 free pts
6,800 needed pts - 1,050 free pts = 5,750 pts needed via purchase
5,750 pts / 10 pts per box = 575 boxes
575 boxes x 20 coupons = 11,500 coupons (or ingots)

Idk I usually don't buy into events and if I do, it's only with coupons. I was doing the math for my own curiosity and for a friend