The TeX syntax highlighter that I use colors all occurrences of a number followed by " in", e.g.
0 in or
32 in in a dangerous bright red, in almost all contexts. Why?
I don't know about Vim and its TeX/LaTeX syntax parser. It probably uses some rule that interprets a number followed by one of the keywords
ex (and maybe also the other units of measure accepted by TeX) as denoting lengths; this is usually good, but it fails in situations such as
There are 42 books on the shelf and still 32 in the box
My flavor of Emacs+AUCTeX (Aquamacs) doesn't do this: it highlights lengths only in the argument of