The Great Gatsby, just three years

I'd like to know of "just" in the following excerpt from The Great Gatsby means "only" or rather "exactly":

“My house looks well, doesn’t it?” he demanded. “See how the whole front of it catches the light.”

I agreed that it was splendid.

“Yes.” His eyes went over it, every arched door and square tower. “It took me just three years to earn the money that bought it.”

Thank you.