2.1.1859 Part 4 Section 184.108.40.206, rSp (Row Spacing)
a. The standard says rSp is used only to set row spacing in equation arrays even though it is also allowed as a child of the matrix element.
In Word, rSp is used to set row spacing in both equations arrays and matrices.
b. The standard says if this element is omitted, single line spacing is used.
In Word, if this element is omitted, the default is 0.