In Newton's Law of Cooling, what does the constant Ts stand for?

1. A cooling object levels off at the temperature of the air around it. 2. That levelling off is a horizontal asymptote in the model, and its height is Ts. 3. So Ts is the surrounding air temperature. 4. The starting difference between object and air is the constant A, not Ts. _Source: OpenStax Precalculus (CC BY 4.0), section 4.7 Exponential and Logarithmic Models_