I have a GW-M850 with the rally timer and would like to actually start using it despite having the watch for years always skipping that segment. I can't seem to get it to just do 30 second intervals as it has minutes and hours. If anyone would know how to set this up I'd be kindly abliged. Basically with HIIT training you want to wor as fast as possible for 30 seconds and then 30 seconds of rest and so forth for as many times as needed. So every 30 seconds a beep would be great.