The time displayed is in seconds so 60 seconds is 1 minute and 120 seconds is 2 minutes.
Swipe up/down to change the reminder time or rotate the watch crown.
For a longer reminder buzz select the high vibration option on your iPhone
To operate with the vibration but without sound you need to put your watch into silent mode. Swipe up from the Home Screen and select the ringer so it looks like this.