yeah I always thought that the words "as soon as possible" were a poor choice in this rule.
My manager seriously flies off the handle when anyone uses that term since is sooo subjective.
I had a coach who gave us some idea.....
If you have not started to take action to take your pen in the time it takes you to look at the mainsail; look upwind and down, tell the crew and then start; you are in danger of not being quick enough. (this was for Ollies / worlds sailing).
It essentially menas you have time to look for a place to do the turn adn then DO IT NOW. More than 10 seconds to start doing something and you MIGHT get a DSQ.