Hmm, maybe the README is a little out of date. I think those are the two final values of hot and cold. In my version, they are actually (-)0.87730401 and 0.95644174.
I think this example is just meant to illustrate how the thermostatting of regions works. If you want to measure an accurate thermal conductivity, you can’t just take the two end points of the energy supplied to the thermostats. We usually determine dQ/dt by fitting a straight line.