I assume you are referring to the Christina Bible, if so, this issue, just like every other issue the bible touches is vague and debatable. Biblical inerrantists (A.K.A. apologetics) will argue that the versus in the bible should not be taken literally -- the tried and true way religious fundamentalists use their "sacred texts" to satisfy their own needs.
I found an interesting article that might help to explain more about your question.
Nobody got "the idea that the Earth was round and not flat" from the Bible.
Everyone learned in Columbus's day knew the Earth was round, and had an idea of its size (hell, the ancient Greeks calculated it). Columbus simply proposed an (incorrect) estimation of the circumference, by which he thought he could reach India. He was incredibly wrong, and was lucky that there was an entire continent in his way to India.
Columbus died thinking he'd landed in India. Poor deluded fool.