Here’s a clue why …
The problem with number fields, entering a static number turns the expression into static and prevents dynamic expressions. So you need to start with a dynamic expression that returns a number. This can get it to work, but is hard to understand later if the expression isn’t related to the calculation.
You could do, for example,
RemainingVotes = VoteCount - VoteCount - VoteCount + 11
When you maintain this later you’d say “What does this even mean?” haha