In Ether 6:11 we read how long it took the Jaredites to reach the promised land:
And thus they were driven forth, three hundred and forty and four days upon the water.
While this may sound like a random number, John Welch notes:
Certain things that might at first have appeared outrageous, on closer inspection have turned out to be right on target. The ancient Jaredite transoceanic migration that lasted 344 days (see Ether 6:11) ceases to seem so fantastic when that turns out to be exactly the length of time it takes the Pacific current to go from Asia to Mexico.– John W. Welch – “The Power of Evidence in the Nurturing of Faith,” in Echoes and Evidences of the Book of Mormon
If Joseph Smith was guessing, wouldn’t he have likely been wrong by quite a large margin?