The hour counter at the bottom will be halfway between 0 and 1. So you add the 30 minute counter to the hour counter (kinda, if you’re at 55 minutes the hour counter will nearly be at 1) and then read the seconds from the big hand (the seconds subdial on the left is the running seconds, not the chronograph seconds).
Haha. If the chrono has been running for 55 minutes, the minute counter dial will read 25 minutes (ie, 30 + 25) and the hour counter will be nearly at 1.
The hour counter at the bottom will be halfway between 0 and 1. So you add the 30 minute counter to the hour counter (kinda, if you’re at 55 minutes the hour counter will nearly be at 1) and then read the seconds from the big hand (the seconds subdial on the left is the running seconds, not the chronograph seconds).