Rowsbette... the best way to look at it is longer term.

It makes more sense (to me anyway, that way...) it's not 500 calories today... it's 13000 a month...
If you burn more than you eat by 500 calories per day, that's 3500 a week, or 1lb of weight, or 4.3lbs a month (2 kilos, give or take), or a mammoth 52lbs a year - nearly 4 stone!
I'm going for about 1000-1250 a day just now, which'll come down to 500-750 as I get nearer my target weight.