A round being 6 seconds seems too low

Recently I had my players go up against a dragon, and it was a really cool, climactic boss fight. It lasted a full 5 rounds, and felt like they had spent so long trying to take this thing down, and we all celebrated when they finally killed it. Then I thought about it a bit and realized 5 rounds would only be 30 seconds, which means canonically they rolled up to a dragon lair and beat this thing to death within half a minute. It makes it feel a lot less cool and climactic when you think of it that way lol

I should clarify, I don’t have an actual problem with the rule, I just thought it seemed funny that they killed it so fast if you look at the actual in game time

EDIT: To everyone saying “it doesn’t matter”. Yeah, I know? I don’t actually care, I just thought the discrepancy between player perceived time and in game time was weird. Thanks so much for your input