2.1.151 Part 4 Section 2.4.41, tblCellSpacing (Table Cell Spacing Exception)
For additional notes that apply to this portion of the standard, please see the notes for bottom, §2.4.2(a, b) .
a. The standard states that any width value of type pct or auto for this element shall be ignored.
Word uses a default value of 0 for the width when the value of the type attribute is pct or auto.