COP depends on the temperature difference.

A single COP is some yearly average usually but in these measurements it is probably a shorter period.

In europe there is a somewhat more rigorous measure of Seasonal COP (SCOP) where the typical climate (in my case nordic) is taken as a standardized test. So x number of days outside temp 0C, y -5C, z -10C, w +10C etc.

So in case of Air source heat pump if the outside temperature is +10 or +15 you can easily get COP numbers that are 9 or above.

Better technical documentation usually has rated COP for some different outside temperatures or even a graph.