When we talk about the "compressed volume" of the Earth's atmosphere, we're referring to the hypothetical scenario where all the air in the atmosphere is brought to Standard Temperature and Pressure (STP) conditions, which is defined as a temperature of 20°C (293.15 Kelvin) and a pressure of 101.325 kPa. Under these conditions, one mole of an ideal gas occupies 22.4 liters (0.0224 cubic meters). The calculations we made earlier determined how much space the entire mass of the Earth's atmosphere would occupy if it were compressed into a sphere where every bit of air is at STP. This provides a conceptual way to understand just how much air is actually surrounding our planet when it's spread out in its natural state (where temperature and pressure vary greatly with altitude).