1. Once you have selected a Google Sheet as a resource (learn here how), you can create 3 types of subscriptions depending in the range of cells you select in «Sheet Rules».
2. In «Range» you must select the range of cells you want to receive notifications about, following the A1 Notation, as shown in the picture below.
3. If the range of cells you select have «date» format, certain options will appear in «select an operator». Regarding the configuration I created in the picture below, I will only be notified when a date greater than «12/1/2019» is added to that range of cells.