vb.net – Why Visual Studio weird behaviour in immediate window (although resolved)?

It seems that the immediate window anticipates the execution of the code. It took me a while to figure out what was happening.
In the following code example the variable A in the immediate window did not change the sign of B:

B = 2
A = -B
' debugging to this point the immediate window was showing A = 2
...

But, really, where the sign was changed was in a later call:

....
My_Update_Method() ' the problem was here (changing the sign of A from -2 to 2)

I wonder why this ‘anticipated’ behavior. Can anyone help me with the answer?