Custom menu widget problem

I created 8 custom menus. The documentation online says, “4b. If you want the menu to appear in your sidebar or other widget area, go to Appearance > Widgets, add a Custom Menu widget, select the menu from the widget pulldown, type a title, click Save.” However, when I go to to the custom menu widget, only 6 of them show up in the drop-down menu, so I can’t insert the last two menus (each created for a different page). Am I doing something incorrectly? I was able to insert the other 6 menus in their respective pages.