GetFieldSelections() will return a string that look like in the current selections object. This means that it will look like the actual search string, if your seleciton is search based. It will also turn into "9 of 152" format when you select multiple values and the seleciton string is too long to display.
If you want to show the actual selected or posible values in the text object, you need to use Concat() function instead.
=Concat(DISTINCT Agency_Name, ', ')
If you only want to show the values when there is a selection you need to find a logic for that.