2.1.1169 Part 1 Section 19.5.56, pRg (Paragraph Text Range)

a.   The standard places no restrictions on the values of the st attribute and the end attribute with relation to one another.

PowerPoint requires the values of the st attribute and the end attribute be equal to each other.

b.   The standard places no restrictions on the values of the st attribute and the end attribute with relation to the paragraphs.

PowerPoint requires that the st attribute and the end attribute be less than the number of paragraphs.