You have list  of selectItem that you refer them as
{adevertisementCategoryDataAction.componentList}
that each of that (SelectItem Object), have lable (as String) and
value (as Object),
that this list bind to your component and on other hand you have one
property (selectedAdvertisement.title) for selected index.

i think the problem  here is your {selectedAdvertisement.title}
property type, is not equivalent to SelectItem value property type, so
can not bind properly and always select the first item of SelectItems.

i mean if your value property type in your selectItem (componentList)
is Long
the title property on selectedAdvertisement must be Long.