Thanks, Dave,
It worked just as you said.
Besides my two internal hard drives there was another volume there in /Volumes, but I have no idea how it got there. It had the name of one of my external backup disks from a previous backup. I deleted only that one and the disk size went down to what it should be.
By the way, I did not realize I'd posted to two places. I am new to forums. Sorry about that, and thanks again for your help and the terrific product.
john