Hi I am trying to sum the value of total_msg_send of these objects, the first sum is good but in the rest of them it sums the previous result with the result of the next sum

This is the code that I have

this.groups = rsp['cards'];

 for (let index = 0; index < Object.keys(this.groups).length; index++) {
  const element = this.groups[index];
                
    this.apiSvc.receiveMessages(element.id).subscribe((rsp: any) =>{
      console.log(rsp); //object
      rsp.forEach(element => {

        this.sum += parseInt(element.total_msg_send);                
      });
        console.log(this.sum);//sum
                    
     });
                
 }

I'll appreciate if someone can help me, thanks