Smart Dimension, Not Acting Smart

Hey, I just started my first tutorial on SolidWorks.  I got as far as sketching the circle.  The tutorial says to smart dimension it, so I do...  but it doesn't work right.  There appears a giant diameter symbol, no numbers whatsoever, and I cannot drag it around as it says I'm supposed to be able to do.

What is going on here?

SolidworksSketching