x-size X Size of the Glyph

The pixels per row in the bit-mapped glyph that has been declared with a <glyph-data> element as part of a <private-char> element.
OPTIONAL on element: <glyph-data>
Value Meaning
A number An integer number of pixels, for example, “45”, that is the number of pixels in each row of the bitmap of the <glyph-data> element.
Restriction @x-size is an optional attribute; there is no default.
Tagged Sample

Pixel count each row of Arrow glyph bitmap

<private-char name="NORTHWEST SOUTHEAST ARROW" description="Arrow,
  normal weight, single line, two-headed, Northwest to Southeast">
 <glyph-data id="NWSEArr" format="PBM" resolution="300"
   x-size="34" y-size="34">