2.1.176 Part 4 Section 2.4.73, top (Table Cell Top Margin 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 the value of the type attribute shall be assumed to be dxa (twentieths of a point) when it is omitted.
Word ignores this element when this attribute is omitted.