fireball is correct, arrows is not.
i just had a chat with our designer about this as i was interested!
it is still incorrect, but i thought it was a pretty fun bit of 'behind the scenes' info!
he drew this beautiful diagram for me to explain...
basically when we released monk, we had to change arrows. monk would reflect the entirety of arrows even if he was on the edge of the circle, which felt bit unfair.
what we did then was divide arrows into several different hit areas, so that monk could deflect the arrows from one of these areas, BUT the rest of the areas would still damage any units below.
so the middle of this new circle/the radius of a little circle is probably where the 1.4 radius is being calculated from.
we'll add it's proper radius to our list of bugs.