DR+0.2 says your machine that "she" have to think that your tool diameter is bigger...
I believe radius +0.2mm and diameter +0.4mm
is the same with the Toollength ... DL+0.2 = Toollength +0.2mm
when you type -0.2 "she" think it's smaler... so easy...
You can type it in the Program for a quick correction of your tool...
But I don't use it because it's just confusing.
I'd rather just use the tool list.