If you take population into account, it's probably about the same amount of people getting each game. Just a guess. (Actually, the PSU/MSU game might be getting more potential viewers than any of the others?) Still, it's cool that people from Nevada to North Carolina and North Dakota to Texas can see us over the airwaves.
I think the percentages listed to the left of the key on the map indicate TV households...so 34% get PSU/MSU, 28% get ISU/KSU, 20% get UM/VT, and 18% get Cal/UW. Although the geographic area for the ISU game is far wider...the population of the geographic area getting the Penn St. game is enormous...including both NYC and Chicago.