Hi Liana,

You are reading that in the help for a surfaced-based analysis example.
That text is there because blurring is different in the volume from on the
surface. In the volume an 8 mm blur would be added (with that option).
On the surface, the resulting estimated blur would be 8 mm.

Basically, forget the text for any surface example, and stick to that of
the volume. In the volume, '-blur_size 8' would add an 8 mm blur, just
as you want.

- rick