Interesting case. What is crystal clear is that it cannot be a push, no matter what happened.
I think 5Dimes did indeed grade it properly. However I come to that conclusion after reading everyone's interpretations.
I think the prop should have been written more clearly.
A fair compromise would be to refund the $923, in this case,only. Then in the future 5 Dimes should offer a little explanation of the bet, right where the lines are posted. The problem is every bettor will want that loser refunded, now. The poster had to go public, but ( in anger), used a poor choice of words.
I believe the poster was given wrong info by a clerk.
Very tough case ! It won't scare me away from 5 Dimes.