Offsets. This particular object is represented in gnumeric's XML as
four doubles, space separated. Presumably, each represents an
offset in a particular direction -- top, bottom, left, right -- but
what the reference is for each offset is not known, nor is it known
which one is top, bottom, left, or right, or even whether that's
the correct interpretation of the numbers. This is an area of the
gnumeric XML that is not terribly well documented even in their
code, and I don't think the features that use offsets are terribly
mature yet.