What is Kc at its temperature?
It is unanswerable. Kc is not a standard abbrivation such as deltaT, or S, or c(the speed of light).
I have seen Kc used sometimes as the equilibrium constant, but not often. More often, equilibrium constant is Keq.
Language is that which we make it. In the USA, there is a tendency to make up words, and symbols, and expect all others to understand the meaning.
In a pig's eye, it will stop.