Ionic3 slider.length() gives wrong number

Hi All,
I have two ion-slide on a page. when i try to get the current index and lenth of the total slides the output is wrong. I have an array of length 3 in which 3 images are there but length is shoeing 5. The code for my both slides are as

 <ion-slides #firstSlide (ionSlideDidChange)="slideChanged()" autoplay="6000" speed="300"
      <ion-slide *ngFor="let img of totalSlides;let i=index">
        <img src={{img.ImageForMobile}}  (click)="goToUrl(img.RedirectUrl,i)" >

and for second slide

<ion-slides #secondSlides (ionSlideDidChange)="slide()" autoplay="2000" loop="false" speed="300"
    <ion-slide *ngFor="let img of secondArray;">
      <img [src]="img.FilePath" alt="">

Ts is as

  @ViewChild('firstSlide ') firstSlide : Slides;
  @ViewChild('secondSlides ') private  secondSlides : Slides;
   console.log('length of bannners',this.promotionalSlides.length());
  let currentIndex = this.promotionalSlides.getActiveIndex();

when i try to find length and current index both are showing wrong. Length is showing 5 instead of 3 and current index goes upto 4 instead of 2

plaease help one slider loop is true and one slider loop is false