Ion-select select default value not working

I have ion-select with that have many options and I have when the view is ready to select one default value depending on CurrentNumber. i have this code:

<ion-select formControlName="Level">
          <ion-option [value]="" *ngFor="let level of levels" [attr.selected]="(level.levelNumber == currentLevel)? true : null">

this.currentLevel = 1;
the data comes from the server like that :

data = [
  levelNumber : 1,

The selected attribute is ignored if the ion-select is bound. You must assign to your backing FormControl instead to set the initial selection.

yes i put the value in the formControl when the values ready.