Not sure I've seen this anywhere - I just hope I'm doing something wrong, but I can't quite seem to get the equation editor to do what I want.

I'm using an equation to drive an array.  I need to equally space some slots between two other slots on either end.  What seems to be biting me in the "hiney" is my calculating the count of slots:

Maybe there's a better way, but it works - inspite of the triangle with the exclamation point in it.  If I hover over that, it reads:  "Unable to compute value. Invalid entry."

Is this just a quirk of the equation editor or is it a fluke it's working? 

I'm a little reluctant to push this into production with knowing for sure.

BTW - SolidWorks2012 x64 SP3.0

Thanks