BTBSIGN 2.3" Programmable LED Interval Timer Countdown Clock Stopwatch You can set several groups of training time and rest time.Like 4 Times 1 minutes Training and 30 seconds rest Set as this: F1 01:00 C1 00:30; F2 01:00 C2 00:30; F3 01:00 C3 00:30; F4 01:00 C4 00:30 It also can countdown anytime to zero like countdown 1 hour to 0 or 15minutes to 0 Stopwatch counts up to 99 minutes, 59 seconds and hundredths of seconds 40 secs for exercise then 20 secs for rest and repeat two times. Setting: (F1 00:40 C1 00:20; C-C - 02) 1st step: press digit 1 button to interval timing mode, timer show P1. 2nd step: press  F-A button and input 00 40, press enter to save 3rd step: press C-U button, and input 00 20, press enter to save 4th step: press EXIT key to set repeat times.Input 02 and then press enter to save all the setting. Final step: press START key begin to run