Everything is working as it should. I think you want tempF(68) and tempC to get the result you expect. The notation degF means a temperature difference. See the manual for details.
On Mon, Apr 13, 2020 at 07:49:51PM +0800, 積丹尼 Dan Jacobson wrote: > X-debbugs-Cc: adri...@gnu.org > Package: units > Version: 2.19-1 > > $ units 68degF degC > * 37.777778 > / 0.026470588 > > Should be around 20. > > $ units degC > Definition: K = 1 K > > $ units degC degK > * 1 > / 1 > > What?!