What does it mean if someone's number of friends on Facebook is different than the number actually shown?

[Sleeping]

For example, if under number of friends it says 10, but when it shows the list of friends there are only 9. Do they just have 9 Facebook friends, or is one not appearing? If so, what would cause this? Thanks!

[kaire]

The numbers don't match because some of those person's friends have set their privacy settings to "Only friends." Since you aren't friends with those people, you won't see them on other peoples' friends lists.

For example: you notice your friend Jane has 80 friends. But when you click on her friends list, you see only a list for 72 friends. That means 8 of Jane's friends have changed their privacy settings to "Only friends" and since you aren't friends with them, you can't see them.

In your question, it means that person has 10 friends, but 1 of their friends has changed their privacy settings. You aren't friends with that 1 person so you can't see them. But that person really has 10 friends, not 9.