I’m currently on day 6 and I am also starting to hit a weightloss plateau. I think the point is that at the start you lose a lot of waterweight because you burn all the glycogen in your body.
If 1 pound of fat is 3500 calories, that would mean that on average calorie expenditure daily you’d be losing 0.7 pounds of fat or so. So it feels like it’s less but actually you’re burining fat mostly and a tiny bit of muscle.