When considering IoT data amounts, sensors transmit very small amounts of data.
For example, the state of a door is transmitted with a binary 1 or 0. With this very small information the state of the door being open or closed can be processed further.
Similarly a water meter has little data to transmit even if it has a reading of 6'972m3. Sensors for Level, GPS Position, Parking, Humidity, Temperature or People Counting are all in the low volume LPWAN category.