2.1.499 Part 1 Section, SEQ

a.   The standard does not specify the meaning of the optional bookmark name in the SEQ field.

In Word, when a bookmark name is used in an SEQ field, the SEQ field displays the result of the SEQ field nearest the bookmark in the document.

b.   The standard says that the \s switch resets the sequence number to the built-in (integer) heading level specified.

In Word, the \s switch resets the sequence following a heading of the specified level.