# of unique opens doesn't match the number of opens listed when I click to see who has opened it.

I sent an email campaign about an hour ago.  On the main page that lists all emails, it says 11 people have opened their email, but when I click to see who has opened theirs, there are 24 individuals listed that have opened their emails. (I have it set to unique opens).  Just curious why those numbers differ when I am only tracking unique opens.  Seems like those numbers used to pretty much match in the past.  Even on that page where it lists the individuals that have opened theirs, it says 11, but 24 different people are listing and show the time they opened it.