One morning recently my wife told Alexa to "turn up the temperature" instead of our normal command "set the temperature to 71 degrees". I expected some message back about how Alexa didn't understand, but instead, she replied "temperature set to 71." That night I asked Alexa to "turn down the heat" and she set it to our normal overnight temperature of 69 degrees. I initially thought that Alexa was remembering our normal daytime and nighttime temperatures, but not the case. The "turn up" and "turn down" just adjust the temperature by two degrees, up or down.
More commands can be found at this link.