The first time you stepped on the scale, it may have been a little kooky- especially if it's a digital one. My digital scale does funny things when I change it's location (it needs to be on a flat, perfectly even surface) or accidentally push it with my foot.
On the other end though, it is definitely possible to lost 10ish pounds. If I'm on my period, I'll drop 5-6 lbs within 24 hours depending on water retention, hormones etc. Couple that with some fat burning and fewer calories, hello massive weight loss