It's so difficult to make a point rather than copy and paste a random link and say "look, it is here. Dont you read?" lol Provide direct quotations oh wait.. you cant.
You asked him to PROVIDE EVIDENCE (your words). In most people's understanding of that request, simply telling you something would not suffice: one needs to link to an authoritative source. If I told you that the people in my town lived to be a thousand years old, and you said "Provide Evidence", I would assume you wanted newspaper articles, census data, birth and death certificates, and the like, not merely me saying it again with different words.
In any case, let's do BOTH. I'll give you the
link to an article which you could read, and I suppose I can read the relevant parts to you: "it was widely known by the 15th Century that the Earth is spherical. The question was, how big is the sphere?...Columbus preferred the values given by the medieval Persian geographer Alfraganus)...That was Columbus’s first error, which he compounded with a second: he assumed that the Persian was using the 4 856-foot Roman mile; in fact, Alfraganus meant the 7 091-foot Arabic mile...Taken together, the two miscalculations effectively reduced the planetary waistline to 16,305 nautical miles, down from the actual 21,600 or so, an error of 25 percent...And then there was the third error...Through a complicated chain of reasoning that mixed Ptolemy, Marinus of Tyre, and Marco Polo with some “corrections” of his own, Columbus calculated that he would find Japan at 85º west longitude (rather than 140° east)—moving it more than 8,000 miles closer to Cape St. Vincent."