It is your data type in access or sql. If you do not use a variable type then the field is always X characters and spaces are padded to the end of data to fit the field.
You can update the field in the DB to a NVarChar or something and then update all of your data to remove the extra space.
Or you can add a rule to your entered data to always concatenate the extra space needed on.
Or I think you could add the normalize function to your filter which would remove the trailing spaces from the list data and let you compare correctly.