I don't know where to find the "more accurate" numbers. I just know that ESPN was saying Ohio State moves into the #1 spot. What time-frame are you using for your numbers? If you're using "all-time" numbers, maybe ESPN is using just the results since the draft went to a 12-round draft, or 14-round draft, or whatever the draft is, nowadays. Or maybe its the other way around.
Edit: looking at that web site, it looks like the draft dropped to 12 rounds in 1977, then down to 8 rounds in 1992 or 1993, then down to 7 rounds in 1994. It's been 7 rounds since then. (At least, that's what it lists for each year. If there are more rounds than 7, it doesn't have them listed.) I'd guess that you're using all-time first-round draft picks, while ESPN's statistics go back to one of those years, for some reason. It doesn't make sense to me, as a first-round draft pick is still a first-round draft pick, regardless of how many rounds you have.