The two circled in red are the "Good Morning" and "Good Night" buttons. If you have the model number of the heater we can try to find a manual online and confirm the function and use. I think you can use the heater safely even if you don't use those buttons at all; they just add extra convenience or functionality.
All the buttons and functions are the same. The only difference is the two buttons on the right. I don't know the details of their function.I told you I will research it for you if you tell me the model number of the heater. What is the model number?