Here is an article from early October, which mentions that the Florida ballots were "so long that voters will have to fill out multiple sheets with races on both sides, then feed those multiple pages through ballot scanners, one page at a time."
And, here (PDF) is a copy of the St. Lucie county sample ballot, showing four pages worth of elections and ballot questions (e.g., 2 sheets, with races on both sides).
And, for good measure, here is a link to the Florida Department of State election results page, reflecting a 70% turnout in St. Lucie county. 70% is, of course, half of 140%, and thus consistent with the point that the 140% number reflects (as the initial report stated) the two "cards cast" by each voter. 70% turnout * 2 cards = 140% "turnout" (measured as cards cast/registered voters).
Disregard my last post... I see a mistake.