a few notes from a professional- I've had patients gain and lose as much as 10 pounds with constipation and a bowel movement. If you aren't used to a high salt diet, you might retain more fluid after higher salt meals.. again- I have seen much larger gains than people expect (my dialysis patients who drink too much have gained as much as 20 pounds in a 3 day period of fluid- generally goal is less than 3% of body weight, but things happen sometimes and some of them are not as compliant as others). yes that amount is more than we can safely remove easily.
Other things that people don't consider: what are you wearing on the scale? is it the same every day? If you have clothing on- are things in the pockets? Even a cell phone impacts weight. My patients weigh themselves publicly at the scales in the clinic. coins in a pocket, keys, different shoes, shorts vs long pants etc are all things that impact the weights and if they change we can leave fluid on or try to take too much off.