var MyCount:TextView? = null

The ? means it's "nullable" which is akin to saying it's a pointer.  Not the same as a pointer but akin to a pointer, meaning that the value of null is allowed.

Later on, if I say MyCount!!.text, I'm saying "I know for a fact that MyCount is not null, so follow the pointer."  If MyCount is null--I lied--and the program crashes.

I declared MyCount as TextView? so that I can initialize it as a global variable without creating a new one.  A TextView? is allowed to be null.  A TextView is not allowed to be null.

So, if MyCount had been a TextView, I would have said MyCount.text without the !! since, in this case, MyCount isn't nullable; it has to point to something, and the !! isn't necessary.