In the Tutorial on the right, you will see how a duel point is counted. Note that when Donald (Grey) is struck the match is over.
Duels do not usually end so abruptly. The first person to get hit loses the match. Sometimes this is up for debate. It is best to appoint an official ( Owen in the background ) over the duel. Allowing this person to make the call if the combatants cannot decide who was struck first.
In the Tutorial on the Left, watch as Roy (red), crosses into Donald's (grey) Attack Zone. This will result in a penalty. Roy will either lose all of his armor, all but 1 health, or be sent into recovery.
Notice, even though he only breaches the Attack Zone for a second, the penalty is still counted.
In the Tutorial on the right, See how the ball is bounced by Roy (red). Then struck with the edge of the Rune Sword. This sends the Ball into Donald's (grey) right leg.
This is a point against Donald.
Also note that Roy has crossed into Donald's Attack Zone. This will result in a penalty.
In the Tutorial on the LEFT, see how combatants fight for the Ball. Donald (grey) manages to send the ball back to his Attack Zone. This ends the fight for control. A duel can still occur where a player takes damage.
Once in his Attack Zone, Donald cannot be damaged from a Rune Sword. Roy (red) then backs off in order to defend his goal.