如何获得剑道网格的行数

Question

<mat-tab-group mat-align-tabs="start" animationDuration="0ms">
  
    <mat-tab>  
              <ng-template matTabLabel>
                  <span matBadgeOverlap="false">Source</span>
                  <div> 4  </div>  
              </ng-template>

    </mat-tab>

    <mat-tab label="For Action">Content 2</mat-tab>   
</mat-tab-group>

我想动态地更新那里的行数，而不是“ 4”