Add Range Selector in Text by Script

Yes, you are absolutely right. I wrote it incorrectly. Moreover, I need to manage it using indexes.
Despite the fact that I tried ADBE Text Persent Start and
ADBE Text index Start, it did not give me a result and returned null.
Using alert(rangeSelector.property(4).isModified); I found out that the properties are hidden and I do not know how to work with them.

Here is an example of my code.

var animator = textLayer.property("ADBE Text Properties").property("ADBE Text Animators").addProperty("ADBE Text Animator");
    var rangeSelector = animator.property("ADBE Text Selectors").addProperty("ADBE Text Selector");
    var fillColor = animator.property("ADBE Text Animator Properties").addProperty("ADBE Text Fill Color");
    fillColor.setValue([1, 0, 0]);

rangeSelector.property(4).setValueAtTime(1, 6); 
rangeSelector.property(5).setValueAtTime(1, 12);