Jaybe I am not sure if this will work but nothing ventured nothing gained. Use this line in place of the other on like it
   <Element>
    <Position X="209" Y="213"/>
    <Select>
      <Value>(L:minusfuel,bool) if{ (L:minusfuelcount,number) 1 - (&gt;L:minusfuelcount,number) (L:minusfuelcount,number) 3 == if{ 0 (&gt;L:minusfuel,bool) 0 (&gt;L:minusfuelcount,number) } } (L:minusfuel,bool)</Value>
and then the rest of the code .
Not sure but you might have to use a different perameter other than (L)

This is basically the same thing you had but in reverse instead but in theory should work the 1+ adds so the 1- should subtract. I used minusfuel instead of addfuel just to keep things clear as to what it is doing.
 Hope it helps I am not a expert at XML but I use to be a programmer so I have an idea of what it is doing .