What does Huck mean when he says, “I ain’t everybody”?

In Chapter 35, Huck lives with the Widow Douglas for three weeks until he “turned up
missing”. When Tom finds Huck hiding out, Huck explains that, “It ain’t for me; I ain’t used to it.
The widder’s good to me, and friendly, but I can’t stand them ways.” Huck continues by explaining
all the elements of society he doesn’t like. Tom says, “Well, everybody does it that way, Huck”, to
which Huck responds, “Tom, it don’t make no difference. I ain’t everybody...”(Twain 200-201).