No worries
Only reason I say that is because I check my weight at least 3 times a day and I factor in various things, like weight of food that I eat, whether I've visited the gents (to put it politely), and also to monitor whether certain food/ingredients might slow me down. One example would be where last monday morning I weighed in at 14st 5, but I hadn't eaten much the week before. That night I had a massive kebab, which was also breakfast tues morning. Tues night I had a massive curry ...so by weds morning I was 14st 8/9.
So this morning I found I'm 14st 5 again (albeit stable rather than bordering 14st 6) hence 1/2 lb loss ...but I had eaten more last week - so it's taken into account. See where I'm getting at? I know you didn't have much last week but there's various factors, like as you said - you just had breakfast so you could have been on the lower end of a number this week and higher end of a number last week.
I'm probably not making sense but you might be suprised tomorrow morning. Would be interested to hear