Hello @Mabruna ,
As you can see in the subscribe example code there is a callback; the callback is the function that processes the incoming data when there is any change on your variables. At this video you can see how the callback is modified to parse if the value received is ‘1’ or ‘0’ in the routine to make an action based on that value.
If you wan to monitor more than one variable, just call the subscribe() function again, here is an example to multiple calls to the subscribe() function: http://blog.ubidots.com/digital-piano-with-ubidots-and-nodemcu16, in the example are declared multiple clients but you can subscribe to different topics with only one client too. You should parse the message string in the callback too for knowing what variable changed.