Judging usually takes around 90 minutes after each round.
One episode of Chopped is shot during a 12 hour day of cooking & judging.
While each round is legitimately timed as mentioned on the show, small introductory steps like bringing water to a boil, preheating the oven, and preheating the cooktop are taken in advance in order to save time.
Before the competition starts, each chef gets a 10 minute walk through the kitchen. This is so they know where tools and pantry ingredients are. They also get an introduction how to use the equipment in the kitchen.
Chefs are allowed to bring up to 7 of their own knives to use during the competition.