Weight is not soley bodyfat, it’s everything in/on your body
Water, gut content, stored carbs in the muscle and liver, fat, bones, organs etc
Plus like you said mate, you’ve eaten considerably more food over the space of a few days, and when you say ‘about’ that means we don’t really know how much if we’re being totally honest… it could be 5000, could be 7000?
That in itself would result in approx 2lbs/1kg of weight gain.
On average humans tend to under-report calories by about 40-50%, even registered dieticians typically underreport by 30% or so, we’re just terrible at knowing how much we’ve eaten, so that ‘about 5000’ could quite easily be 10’000, which would explain.
Could it be possible that you had more than that mate?