Honestly don't think OP's exaggerating at all. First off, she's comparing a scale at her doctor's office against her home one. Calibration differences happen easily between the two.
Second, maybe her digestive system had been backed up for days while eating very little, then things finally moved and the number on the scale shifted.
Third, could be fluid retention from salty food the day before that's now worked its way out.
Fourth, hormonal cycle timing.
Your logic makes sense on paper, but it skips over everything else that can swing a scale reading. Sunday I weighed 184, spent the whole day traveling, ate just one meal, a sub with fries on the side. Was parched from all that sodium, so drank a ton of water, that's literally all I had plus some cardio, and Monday morning the scale read 189! Back down to 184 again this morning. Looking at my actual calorie intake, there's no way that accounts for a genuine 5lb swing either direction in that window.
I'm confident something similar is going on with OP. Most likely that earlier reading just wasn't accurate. Also, starting from a higher weight tends to mean pounds drop off quicker, fortunately.
OP, grab a smart digital scale from any general retailer online. The companion app can build a log automatically for you