PM does not update the data usage constantly. In fact, it only update it twice a day.
So, any entry you see is just a total usage between that timestamp and the timestamp of the previous entry. The early morning usage you see on the Usage log does not mean it was used in the morning but a total usage for the last 12 hours.
Also, for correct usage reading, always use Incognito mode to login My Account to avoid reading cached old info