-1/5 seats?

This question has been asked in another thread titled "Glitch in the System" under the Events category, but perhaps the thread title wasn't specific enough. 

Two events that I am registered for show -1/[total number of seats] remaining.  What does this indicate?  Will someone need to be turned away?

I would hate to pay for an event, which prevents scheduling other events during that time period, and find out that I don't actually get to play - particularly when I have been coordinating events with my husband.