Setting elements in a priority list is not straight forword when appending and setting at the
end boundary. When appending without an offset (a null offset), the item will be added at
the default priority. The item may not be the last item in the list. When appending with an
offset equal to the count of the list, the item will get be appended with the last items priority.
All together, when setting the location of an item, the item stays in that location, but appending
an item into a priority list doesn't mean the item is at the end of the list.