Regarding struct initialization list in C++

I am new to C++ and have some query related to below code snippet

1. How to initialize the members of struct trackcmdtime using "struct initialization list - AlertTrackingState() ?

   typedef struct trackcmdtime {
      uint64_t arrive_time_ms;
      uint64_t diff_ms;
   } TrackCmdTime;
   
   
   Class Port {
   
    Public:
    .........
   
    Private:
   
     struct AlertTrackingState {
       Mutex mutex;                            
   
       RejectAlertTrackingList list;  
       uint32_t list_count;
   
       uint64_t req_time_ms;
   
       TrackCmdTime track;    // **Quest-1**
   
       // Initializer
       AlertTrackingState() : mutex(), list(), list_count(0), req_time_ms(0) {}  
   
     } _alert_tracking_state;
   }
   
    // Constructor
    Port::Port() :
      _alert_tracking_state()
    {
      ........   
    }