Be careful of "facts" found on the internet. Especially if they contradict each other:

FACT: Every year, people in the United States use a gun to defend themselves against criminals an estimated 2,500,000 times- more than 6,500 people a day, or once every 13 seconds.
* Fall 1995, Journal of Criminal Law and Criminology
This means that, each year, firearms are used 65 times more often to protect the lives of honest citizens than to take lives.

FACT: Of the 250,000,000 annual self-defense cases using guns, more than 7.7% are by women defending themselves against sexual abuse.
* U.S. Dept. of Justice, Law Enforcement Assistance Administration,
**** Victimization in 26 American Cities, 1979


Is it 2,500,000 or 250,000,000?

The second number is 100 times higher than the first and you'll find this same exact quote in all kinds of places.

Or maybe the number of self-defense cases using guns dropped by a factor of 100 between 1995 and 1979.

if 250,000,000 is the real number and you also believe the stat that there are about 250,000,000 firearms in the U.S. then on average each firearm will be called upon once each year to defend its owner.

Right.