How can I have lost 5 lb over Xmas (in 4 days) ?

How can I have lost 5 lb over Xmas (in 4 days) ?

I’ve been on a really healthy diet for about 6 months- losing weight very very slowly (have probably dropped about 14lb and a dress size). Anyway, I thought I’d let go a bit over Xmas-so I’ve basically been eating chocolate crisps plus cheese & crackers non stop. Not really any main dinners but no exercise either. Anyway- I weighed myself today and I’ve lost 5lb ! I don’t get it since I’ve just been eating fatty rubbish.

Any ideas…other than my digital scales are broken ?