From the rules, a bigger number does not seem to correspond to victory, otherwise it would be a simple game lol.
Therefore, my guess is that the number corresponds to a certain hand, where the number displayed represents the totals of that poker hand. So, in the example, a hand like 6 would represent a hand of 4 aces and a 2. In this case, the 6 would represent a four of a kind.
If we were to go by that logic, then perhaps, we can identify each hand in both player's hands. However, this still does not account for Nowa's warning of the calamity yet. Perhaps there's a trap that's hidden behind the numbers...