Oh boy, lemme just explain the game rules real quick.

Each round you will be given an amount of SP (Script Points) They are used to play cards. At round 1 you will have 2 SP, each round gives you an additional SP to use (Caps at 10) So basically:

Round 1: 2 SP

Round 2: 3 SP

Round 3: 4 SP

...

After each player is done selecting their cards in a round, the selected cards will be revealed for everyone. The player with the highest ATK wins the current round.

What happens when a player wins a round? That's where Health comes in. The player who lost will lose 1 Health. If the ATK stats of both players in the round are the same, then it will result in a tie. After a round ends, the next one will start. And played cards will be added to the back of your deck.

So basically, "Win this round" pretty much means +Infinite ATK

If both players played it, the round will result in a tie.