And remember - radio-locator still overstates the useful nighttime coverage of most AM stations. The inner (red) contour on the R-L maps represents 2.5 mV/m, while the outer (purple) is 0.5 mV/m. Looks pretty, sure...but:
The only number that matters when looking at an AM station at night is the nighttime interference-free contour - how much signal does the station need to be giving a listener to overcome everything else that's coming in on the same frequency from elsewhere via skywave? That number is different for every station. Only for class A stations like WHAM and WGY is it as low as 0.5 mV/m - in other words, only for those stations can the purple contour be said to represent any kind of vaguely usable signal in the real world (and even that doesn't take into account the interference WHAM gets from Cuba on 1180.)
For WKAJ, the magic number is 13.872 mV/m, a figure determined mostly by the incoming interference from KMOX. If you're not within WKAJ's 13.8 mV/m contour, you're probably going to get interference to your reception, making it less than satisfactory.
Needless to say, if R-L plotted WKAJ's 13.8 mV/m inside the 2.5 and 0.5 contours, it would be pretty tiny indeed. According to WKAJ's own FCC filings, it encompasses the village of St. Johnsville and doesn't get more than a few miles beyond it on route 5 east or west. It doesn't reach Little Falls or Fort Plain/Nelliston, nor does it get north even as far as Dolgeville.