Okay, here is a simple explaination (using very round numbers, okay? nobody hit me for missing by a few bits here and there).
A 10MPS connection can flow about 3200gig a month give or take a bit. If you are running 1886 gig per month, you are using about half of that, give or take, so about 5.5mbps. However, the reality is that your dataflow isn't consistant over the day, going higher and some points, lower at others. So you may have moments when you are using a full 10mbps and other times when you are using only 3 or 4.
Gigs of bandwidth is measuring how much went through the tube. MBPS is measuring how big the tube is. Size of tube X time = possible gigs flowing.
I am sure someone more technical will correct me and make me look silly, but hey...