There are two possible reasons target temperatures change. 

The first possibility is that you’ve made a manual change (override) on the thermostat.

Manual overrides are temporary. So, when your next scheduled interval occurs, the thermostat reverts to the set point schedule created in your portal/mobile app. If you would like to make a permanent change, please login to your account and modify your schedules, templates, or intervals.

The second possibility is that your energy service is always looking for ways to save you money.   The service is constantly analyzing information from your thermostat, outside weather conditions, your personal temperature preferences based on your set schedule, and any manual adjustments to the thermostat. The service then makes slight adjustments to your settings to maximize energy efficiency while ensuring that your home’s temperature stays within your comfort zone. These are temporary adjustments causing the thermostat to display a temperature that may be different from the temperature(s) you’ve chosen.