I crap best at 21 degrees C

This picture was taken in my parent's bathroom. The device at the bottom is a digital weather station - a common enough thing to have these days I guess (though the bathroom may be an unusual location for such an item). The handwritten card above has a Celsius to Fahrenheit conversion chart, which is a bit weirder. But check out the bottom of the card. My dad has the specific measurements for both a furlong and an acre. What the hell is going on in that bathroom?