Okay, I'm pretty comfortable using MoI these past few months. But this one's got me baffled...

I'm trying to place a polygon by center and then key in the circumscribed radius. Any time I try to key in a distance (from the center point) the keyin goes to the number of sides field. Even trying to place construction lines and repositioning them, any keyins end up changing the number of sides.

What on Earth am I missing?!?