Use a full clause.

Author: dstein64

doc/startuptime.txt

@@ -61,9 +61,9 @@ Arguments ~
 * `--sourced` and `--no-sourced` specify whether to use 'self+sourced' timings
   for sourcing events (otherwise, 'self' timings are used).
 * `--tries` specifies how many startup times are averaged.
-* `--` is followed by space-separated arguments to pass to `vim`; must come
-  last. Be sure to escape spaces (with a leading backslash) that don't
-  separate arguments.
+* `--` is followed by space-separated arguments to pass to `vim`; this must come
+  after any other |vim-startuptime| optional arguments. Be sure to escape
+  spaces (with a leading backslash) that don't separate arguments.
 * `--help` shows this help documentation.
  >
 	:StartupTime