Nine Rings....Ten men wielding them?

[Caunwaithon]

I haven't finished reading the LOTR book series, however, I have watched all of the exteneded edition movies. In it, It says that Aragorn is wearing a ring of power.

Wait....what?

Nine rings gifted to the rulers of men.......

So where does this tenth ring come from? The nazgul are the "Nine Rulers of men".

So is Aragorn using an dwarve's ring? Or an Elf's? Or did he get it out of his package of "Gondorian Fruit loops" one morning?

It is described as-

"Two snakes, wrapped around each other, with emerald eyes"

In the movie.