The actual size is smaller than the shoes of the same size.
Feet are slightly smaller in the morning and slightly larger in the afternoon. That's because the bones between the soles of the feet are connected by ligaments, which will grow with the pressure.
Degree. After a day's walking, the ligaments will become longer and the feet will become bigger. After a night's sleep, the ligament will return to its original length.
Feet are smaller in the morning. But the size difference is not big, generally within one third, so it is not obvious.