Gas time refers to remaining air (gas) left with current gas mixture, measured in minutes. The time is based on tank pressure value and your current breathing rate.
Gas time is also highly dependent on your current depth. For example, all other factors being the same, including breathing rate, tank pressure and tank size, depth affects gas time as follows:
Gas time is a default field in the lower right-hand corner of default dive modes. If you have not paired a Suunto Tank POD, the gas time field shows n/a. If you have paired a POD but there is no data being received, the field shows –. This may be because the POD is not in range, the tank is closed, or the POD battery is low.