Miscalculation

So I totally miscalcuated my stationary/stamp cost. I got $87. How? I have no idea, because it's $217.46, although that does not include the stamps for the entire invite (STD and RSVP stamps, yes). I'm ok with this, though. Thus far, I am doing OK with the budget. I think. It's hard to guess the two really big things- catering and the cake- because I'm not sure what the total will be! I can guess high, though. So I will. Shake it out, shake it out. Sigh. Crazyness.