I have trouble understanding the functionality of mat-checkbox 'checkboxLabel()' function

Htmlfile

<table mat-table [dataSource]="dataSource" class="mat-elevation-z8">

  <!-- Checkbox Column -->
  <ng-container matColumnDef="select">
    <th mat-header-cell *matHeaderCellDef>
      <mat-checkbox (change)="$event ? masterToggle() : null"
                    [checked]="selection.hasValue() && isAllSelected()"
                    [indeterminate]="selection.hasValue() && !isAllSelected()"
                    [aria-label]="checkboxLabel()">
      </mat-checkbox>
    </th>
    <td mat-cell *matCellDef="let row">
      <mat-checkbox (click)="$event.stopPropagation()"
                    (change)="$event ? selection.toggle(row) : null"
                    [checked]="selection.isSelected(row)"
                    [aria-label]="checkboxLabel(row)">
      </mat-checkbox>
    </td>
  </ng-container>

  <!-- Position Column -->
  <ng-container matColumnDef="position">
    <th mat-header-cell *matHeaderCellDef> No. </th>
    <td mat-cell *matCellDef="let element">  </td>
  </ng-container>

  <!-- Name Column -->
  <ng-container matColumnDef="name">
    <th mat-header-cell *matHeaderCellDef> Name </th>
    <td mat-cell *matCellDef="let element">  </td>
  </ng-container>

  <!-- Weight Column -->
  <ng-container matColumnDef="weight">
    <th mat-header-cell *matHeaderCellDef> Weight </th>
    <td mat-cell *matCellDef="let element">  </td>
  </ng-container>

  <!-- Symbol Column -->
  <ng-container matColumnDef="symbol">
    <th mat-header-cell *matHeaderCellDef> Symbol </th>
    <td mat-cell *matCellDef="let element">  </td>
  </ng-container>

  <tr mat-header-row *matHeaderRowDef="displayedColumns"></tr>
  <tr mat-row *matRowDef="let row; columns: displayedColumns;"
      (click)="selection.toggle(row)">
  </tr>
</table>

ts file

import {SelectionModel} from '@angular/cdk/collections';
import {Component} from '@angular/core';
import {MatTableDataSource} from '@angular/material/table';

export interface PeriodicElement {
  name: string;
  position: number;
  weight: number;
  symbol: string;
}

const ELEMENT_DATA: PeriodicElement[] = [
  {position: 1, name: 'Hydrogen', weight: 1.0079, symbol: 'H'},
  {position: 2, name: 'Helium', weight: 4.0026, symbol: 'He'},
  {position: 3, name: 'Lithium', weight: 6.941, symbol: 'Li'},
  {position: 4, name: 'Beryllium', weight: 9.0122, symbol: 'Be'},
  {position: 5, name: 'Boron', weight: 10.811, symbol: 'B'},
  {position: 6, name: 'Carbon', weight: 12.0107, symbol: 'C'},
  {position: 7, name: 'Nitrogen', weight: 14.0067, symbol: 'N'},
  {position: 8, name: 'Oxygen', weight: 15.9994, symbol: 'O'},
  {position: 9, name: 'Fluorine', weight: 18.9984, symbol: 'F'},
  {position: 10, name: 'Neon', weight: 20.1797, symbol: 'Ne'},
];

/**
 * @title Table with selection
 */
@Component({
  selector: 'table-selection-example',
  styleUrls: ['table-selection-example.css'],
  templateUrl: 'table-selection-example.html',
})
export class TableSelectionExample {
  displayedColumns: string[] = ['select', 'position', 'name', 'weight', 'symbol'];
  dataSource = new MatTableDataSource<PeriodicElement>(ELEMENT_DATA);
  selection = new SelectionModel<PeriodicElement>(true, []);

  /** Whether the number of selected elements matches the total number of rows. */
  isAllSelected() {
    const numSelected = this.selection.selected.length;
    const numRows = this.dataSource.data.length;
    return numSelected === numRows;
  }

  /** Selects all rows if they are not all selected; otherwise clear selection. */
  masterToggle() {
    this.isAllSelected() ?
        this.selection.clear() :
        this.dataSource.data.forEach(row => this.selection.select(row));
  }

  /** The label for the checkbox on the passed row */
  checkboxLabel(row?: PeriodicElement): string {
    if (!row) {
      return `${this.isAllSelected() ? 'select' : 'deselect'} all`;
    }
    return `${this.selection.isSelected(row) ? 'deselect' : 'select'} row ${row.position + 1}`;
  }
}

I want to understand how the checkboxLabel() functionality is working. I am trying to choose selected rows by using this function, but it is printing multiple times on console the row that I choose.

If I am selecting the first rows, then in the checkboxLabel() function, it is appearing mutiple times, I want to use a particular value from that row and I am unable to do that.