I noticed on the elections statistics area for 1972, John Schmitz is not listed as having come in 2nd in any counties.
However, it looks like at least in Jefferson county, Idaho he placed well ahead of McGovern.
McGovern is listed with 1st or 2nd finishes in 4 fewer counties than Nixon is. This corresponds to the 4 Idaho counties where Schmitz finished ahead of McGovern.
In 1992, the top 3 finishes of Clinton, Bush, and Perot are listed. Perot has one less top 3 finish than the other two, meaning that in one county Perot finished 4th or worse.
It looks like the statistic displayed is the top N finished by the top N candidates, where N is 2 or 3.