At the beginning of this year, I reported to The Sparrow and to you a problem with the Outlook Calendar in 2010 and 2016 versions where the incorrect number of appointments for a specific day was not being reported correctly.
Please note that some of you replied that you were using those versions without issue… so the mystery deepen.
Long story made short - the case has been closed.
I have been told that it is a Microsoft issue and update to either Outlook 2019 or Office365 to eliminate the issue.