I can imagine your reasoning, and am obviously much less familiar than you with the site's various common scenarios and edge cases; however, I think should at least be obvious that the number changed meaning, maybe using some CSS change that is more visually obvious than the appearance and disappearance of the minus sign.
I can imagine your reasoning, and am obviously much less familiar than you with the site's various common scenarios and edge cases; however, I think should at least be obvious that the number changed meaning, maybe using some CSS change that is more visually obvious than the appearance and disappearance of the minus sign.