EABA Powers (Scripting question)

[EightBitz]

I've started yet another project that I'm not sure if I'll make it through, but for now, I'm wondering if I could get some scripting help.

If I'm reading the rules correctly, each power costs 1 point to add to the character. After that, every point spent raises the power level by 2. So in the portal, I set the incrementer to have an interval of 2, and that's working fine. But I'm having trouble calculating the point cost.

The script I'm using is below, and this is what's happening.
Say I start with 10 power points.
I add a power. Now I'm left with 9 power points. (This is correct so far.)
Now I increment the power level. It goes from 1 to 3. (This is also correct.)
The problem is, I still have 9 power points. Going from 1 to 3 doesn't subtract a point from my resources.
After that, it works fine. Going from 3 to 5 subtracts 1 point, then 5 to 7 and so on.

I've tried different ways of coding the script, but I can't get it to work how I want.

And yes, I sometimes miss obvious things.

Thank you in advance.

    <!-- Each power that is added by the user costs 1 point
         Each point spent after that buys 2 points.
    -->
    <eval index="1" phase="Setup" priority="5000"><![CDATA[
      ~we must ignore bootstrapped abilities from races and abilities added via advances
      if (isuser + origin.ishero >= 2) then
         var uval as number
         var cost as number
         uval = field[trtUser].value
      
         cost = (uval - 1) / 2
         if (cost < 1) then
            cost = 1
         endif

         hero.child[resPP].field[resSpent].value += cost
      endif
      ]]></eval>