Zgrid find desired region, what is the radius?

Hi,

when I type this in matlab i get the zgrid plot.

zgrid(0.5,1)

So we at school have now calculatet the radius with:

r=e^(σ*T)=e^(-0.1)=0.9

So the radius is 0.9. But I did not remember what the radius of 0.9 is meaning in that case.

Is that the area with the desired region? Thanks