Her biggest selling song is Stronger, which I think is at around 4.5 million. With the song still going and the piano version getting ready, I think PBP could be #1 next week.
rihmixes
Kworb estimated she only sold around 9k before midnight, so this would be bigger than 66-1 IF she can hold on.
And remember, BB reduced the size of their HDS chart some time ago from 75 to 50, so if she can hold on, it's possible that she can debut at #1 on HDS.
I'm not gonna lie. I listened to PBP after it became a hit and it is really a good song. Hopefully people will understand that good songs can smash also