Total System memory usage parameter in unity memory profiler.

I am new to memory profiling. There are various parameters shown in unity's native Profiler under Memory section like Used Total, Total Reserved, Total System Memory usage. From Those I infer, Used Total is the total amount of memory that is currently in use, Reserved Total is the total amount of memory that is reserved from OS including memory for future allocation.

What exactly the Total System Memory Usage indicate and how is it different from Total Reserved? Also which one of those parameters indicate the game's RAM usage.