In the Civ 5 options menu, you can select how long of a delay there is before the advanced info tooltip appears (on mouseover). When it's set to less than a second, it simply states "0", rather than the exact time - i.e. "0.7," "0.2," etc. When you exit the options menu (accepting the change to , say, 0.5 seconds) it will say 0 still. So, you're sent back to the main menu. Return to the options menu and it will display the exact time it is set at, rather than 0. (So it'd display 0.5) If you change it to something else, like 0.6, it will revert back to 0 in the display. Try it for yourself!