That’s the outer radius =5.4m at 80% without radius talent. Outer radius is very low damage but staggers, even the inspect info shows you the numbers (particle FX is “5m”):
Note: Inspect doesn’t seem to take account radius talent which puts it at 6.89/1.91.
The epicentre, a.k.a. close_radius is the important one, the damaging one and is quite small on the GG making it effectively single target; damage drops off very quickly away from explosions epicentre (and you can see this in grinder by putting mobs close to each other).
Interesting to note radius for special punch, the only radius related change in that it now will work on special?
Radius talent is of questionable use on GG.