After approximately 35-40 purchases:
70% 89 Over PG
20% 92 Over C
10% 93 Over PF
I think, something was really not ok in the formula in this event and I hope, the EA see it and feel it. Maybe it could be a more clear communication, if you say: this purchase will give you a 89 Over PG, 92 Over C and 93 Over PF and every user could have calculated with it during the event.
BTW, I liked this event, so thank you, just that part of the event was a bit "annyoying" and not really "clear".