couple reasons, in any event it was close. i feel sorry for anyone when it happens like this. so when calculating the damage and it goes into the decimals the percentage will be rounded (i.e. 10.001 = 10.00). that being said, you could have reached the round limit (=30) and literally missed it by 1 HP or gotten to 100% at the end of the 30th round and in the event of a tie the defender wins.