Bug with add_menu_page

I’m not sure this is a bug in wordpress or not. I’m using add_menu_page() codex to add a top-level menu page in the dashboard sidebar. Looking at the reference, I left the $position parameter empty (so that my menu appears at the bottom of the structure).

However when I activated another plugin which also uses add_menu_page() but with $position set to 100, my menu page now doesn’t appear at all in the sidebar.

If I understand the API correctly, I’m using it the right way. What value should I use in $position argument so that it always appears on the sidebar and doesn’t conflict with some other plugin.