monitor implementation in C

Question

I've just started studying monitors and condition variables in C and I can't understand how the following code works. I have the following implementation of the wait_condition and signal_condition functions for a condition variable

 struct Monitor { 
   //id of the mutex semaphore for the monitor 
   int mutex;
   int num_var_cond;
   //id of the semaphores of the condition variables
   int id_conds;
   //array of the condition_count (they count number of processes suspended on a CV) 
   int *cond_counts;
   //id shared memory
   int id_shared;
 };
 
 void wait_condition(Monitor* M,int id_var) { 
  M->cond_counts[id_var]=M->cond_counts[id_var]+1; 
  Signal_Sem(M->mutex,0); 
  Wait_Sem(M->id_conds,id_var); 
  M->cond_counts[id_var]=M->cond_counts[id_var]-1;
 }
 void signal_condition(Monitor* M,int id_var){ 
  if(M->cond_counts[id_var]>0){
     Signal_Sem(M->id_conds,id_var);
  }else{
     Signal_Sem(M->mutex,0); }
 }

What I'm trying to understand is when I use signal_condition on a process that was suspended earlier with a wait_condition shouldn't there be another wait_sem(M->mutex, 0) otherwise the mutex has value 1 and the monitor is not occupied

I expected to be another wait_sem(M->mutex, 0) after the wait_sem(M->id_conds, id_var) in the wait_condition to keep the monitor occupied