Move sprite to Center of screen - maths not working

[Mirthrindir]

Hello again.

Another puzzler - I believe it's quite simple to get one's sprite centered - see pics.
But the value always returns as 0 .
If I put in mathematical values, I get the correct answer.
Thoughts?

The top row results in 0.
However, if I look at each value, it has a value, eg, 211.
The first value is greater than the second.
How could it return 0 ?
The second row is basically the same equation, with numerical values. It returns the correct answer.

???

[ABG]

Use a value function for the calculations instead of the global init.

It's too early.

[Mirthrindir]

That seems to have done it. Thank you.