Yikes. That doesn't sound right. That sounds more like the number of private messages sent from all members since Day 1. I think I'll just go and see what it says on my account....
Don't panic, Donna. That's not the number sent from you. That's the total number of PMs sent via the system. When the Private Messenger box was bigger (before the page revamp) it may have been a bit clearer that it was the total number of messages sent. Now that is a bit ambiguous. No wonder you got a bit of a shock.