Warning: 100 emails have just been sent by my@email.com

But when I look at
user-level -> domain email.com -> email accounts
I see that I have sent 100 emails today.

And when I look at
user-level -> domain email.com -> email accounts -> email usage
Show usage from:
Today

I see all the sent mails listed but they are not from today but from the last 18 days.

If I selected Show usage from: this month. I see the same list with 100 mails.

When I selected Show usage from: this month (excluding today). I see no mails.

Why are all mails from the last 18 days listed as todays?