So apparently the character count for forum signatures is not what it says on the profile page

I tried to add italic tags to part of my signature, which used up 7 of my 9 remaining characters ([i][/i]), yet it chopped a character off the end of my signature anyway
I checked elsewhere, I've currently got 246 characters, even counting the double space, so I can only conclude that although it's listed as having a max character count of 255 that it's actually 252
If I go right to the limit where it says "characters remaining: 0" and click "Change profile" it reloads the page, truncates the last 3 characters from the signature, and still tells me I have 3 characters remaining
I don't think I'm
that bad at math so what's going on here