else if jquery not working when scroll window

I tried to use the code bellow for control element when scroll, "if" and "else" are work but "if else" not working, please tell me why, Thanks!

$(document).ready(function() {
        var offset = 900;
        var duration = 2000;
        $(window).scroll(function() {
            if( $(this).scrollTop() > offset ) {
                $('.icon_circle').css("top", "138px");
                $('.row2 .col-left img').css("border", "1px solid red");
            } else if( $(this).scrollTop() > offset + 100 ) {
                       $('.icon_circle').css("top", "168px");
                       } else {
                           $('.icon_circle').css("top", "0");
                           $('.row2 .col-left img').css("border", "none");
                       }
        });
    });