"Message marked as not a spam" after marking it as spam!

Using webmail.verizon.com, I sometimes see a message in my Inbox that looks like spam.  I will often open it so I can see the sender's address and confirm that it's spam, while being careful not to click on any links.  I then click the Spam button.  I then get the message saying:

Marking message(s) as spam.

but right after that the message changes to this:

Message(s) marked as NOT a spam.

I then check my SpamDetector folder and I do see the message there.  Any idea what's happening here?