Column restricted to Dropdown list values but other entries are present


I changed a column to be restricted to dropdown values, but when I added a value to the dropdown list I received a warning that there were several entries in the list that "24 cells in the X column have values not in the dropdown list". Is there any way to detect or highlight which values these are? They all look the same. Maybe there is a space at the end of some or something? I do not want to have to go down the list and select the "same" (yet correct) entry from the dropdown list for all entries...