The red disk defaults to represent 60 minutes. If you’d like to customize the time scale, tap on the overlapping circle icons in the lower left-hand side of the watch face. This allows you to toggle between a custom scale disk and 60-minute scale disk.
Once you select custom, you can select the hours, minutes and seconds you want the entire disk to represent. Tap on each time area (hours, minutes, seconds) to adjust duration using the digital crown.