Exercise 3.1: I Go Round in Circles, "1 unit wide"

[eed3si9n]

https://github.com/underscoreio/creative-scala/blob/develop/src/pages/pictures/images.md#i-go-round-in-circles--

original

Create circles that are 1, 10, and 100 units wide. Now draw them!

circle(1)

problem

If the passed in parameter is radius, then circle(1) would draw circle with 2 unit width.

expectation

I'd think the following would give the circle with 1 width:

circle(0.5)

Am I understanding this wrong?