Its a variable countdown timer, so it'll countdown 10 minutes in its standard configuration, but you can use the bezel to reduce that so if its a 5 minute start or a 3 minute start as they have in high school team sailing races you can do that and it'll countdown from that too. Rather a unique idea as most regatta timers are either fixed to a certain number of minutes or just mark off the minutes sundial.
When I was sailing I actually wore a TAG Heuer F1 Chronograph and because it was quartz, you could actually advance the chrono minute hand (both chrono minute and seconds were on the main dial not subdials) to any point you wanted so you could put it back after a battery change. So I would set the chrono minute hand forward to 57 minutes which gave me a perfect 3 minute countdown to zero to get my puffin pacer in position for the gun.
This Rolex would give much better legibility though which is a real plus, two tone or not its actually quite practical for its intended purpose and well thought out. My only question is whether the pushers are safe to be operated in water because the Daytona's aren't nor are most chronographs.