"The quantity light latched at 102:44:31, and indicated that 5.6% of the original propellant load remained. This event started a 94-second countdown to a bingo fuel call which meant 'land in 20 seconds or abort.' So if the count gets down to zero, Neil will have 20 seconds to land, if he thinks he can get down in time. Otherwise, he will have to abort immediately. If you're 50 feet up at bingo fuel with all of your horizontal rates nulled and are coming down to a good spot, you could certainly continue to land. With your horizontal rates nulled at 70 to 100 feet, it would be risky to land - perhaps giving you a landing at the limiting load of the landing gear. At anything over 100 feet, you'd punch the abort button, say goodbye to the moon, and stew for the rest of your life!"
- ? Feld, 'The First Lunar Landing' transcribed by Eric M. Jones, hq.nasa.gov.