[css3-background]Positioning of box-shadow blurs?

I was reading more through the box-shadow spec, and the part on the blurring
seemed unclear to me. Will the blurs be on the "outside" of the regular
shadow, the "inside", or "centered"? So, if we have a 400px wide box, with a
blur radius of 10px and no spread, will the resulting shadow (from the very
lightest left pixel to the very lightest right pixel) be 400px wide
(inside), 405px wide (centered), or 410px wide (outside)? Inside would have
the effect of lightening the inside of the shadow; centered would be like
"smudging" in bother directions from the otherwise hard shadow; and outside
would be adding extra darking to the area around the shadow.

Also, the shape of the blurs seems to be unclear - I know that some parts
shall be left to the user agents, but the preservation of sharp/rounded
corners should be up to the author, without a doubt.

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no sense or use ridiculous timescales at all has dropped over 164% in the
last 5.62474396842 years.