(scrolled)="onScrollDown()" getting called multiple times - Angular 2

Question

I am using this infinite scroll library & its calling a fucntion miltiple times on scroll my code:

<table class="table table-striped table-hover inline-edit"
    infinite-scroll
    [infiniteScrollDistance]="2"
    [infiniteScrollThrottle]="10"
    (scrolled)="onScrollDown()">
onScrollDown() {
      this.pageNumber += 1;
      this.getContacts();
}

When it reaches viewports length it calls onScrollDown multiple times like 5/6 times