-arguments since they would require lookahead after @code{3}. However,
-if @code{3} gets rejected as an optional argument based on evaluating
-its predicate, it should still be able to participate as part of a unit
-expression in a following mandatory argument."
+arguments in one go since they would require lookahead after @code{3}.
+The predicate is checked after @code{3}, and if it is suitable,
+Lilypond commits to parsing as a unit number, and checks the result
+again. For the predicate @code{integer?} and @code{3\cm}, you would
+actually get a syntax error (since the combination is no longer an
+integer) rather than Lilypond trying to see @code{3\cm} as two
+separate arguments."
+