What stumps me is that the way I see the pot odds is that to call the $10 to win a pot of $25 means the pot odds - as a percentage - is 10/25 x 100 = 40%.

I only get 28.5% (which Stacks & Spoon get) when I work it out by including your own $10 - ie: $10 to win $25 + your $10 you just put in (10/35 x 100 = 28.5%).

BUT one of the first thing I learnt about calculating pot odds is that you NEVER include your own bet. And that is why I see it as calling $10 to win $25, thus 40% and thus my confusion.