conversations.from: human
conversations.value: Mark has 12 candy bars in total between Mars bars, Snickers, and Butterfingers.  He has 3 Snickers and 2 Mars bars.  How many Butterfingers does he have?
conversations.from: assistant
conversations.value: Not counting Butterfingers Mark has 3+2=5 candy bars.
  So Mark has 12-5=7 Butterfingers