It's kind of confusing. Some Class III-As were not protected according to the definition, which was protected to the 2.5 mV/m. The study for the Savannah station at the link showed WIRL's NIF as around 4.5 mV/m, even in excess of the NIF prescribed for III-Bs, 4.0 mV/m. WOW 590 was/is by its present callsign 5 kW nondirectional. At the distance at Kalamazoo, the 10% skywave would be close to 500 uV/m, which would limit WKZO to 10 mV/m NIF, 4 times the prescribed 2.5 mV/m for a Class III-A. The folks at Broadcasting gave up after a number of years and just showed almost all of them all as "III", because the designation was so inconsistent according to the prescribed rules.