An employee can only be owed what they have accrued if they leave part way though the year ie 25 days enbtlemrnt leave after 8 months accrued 16 days already taken taken 12 days during the 8 months owed 4 days at end of employment
You also have to ensure that they have accrued the statutory minimum, e.g. if they are given b/h on top of the 25 days (which I assume they are) 28/12*8=19. 19-12-(any b/h they have taken)=? If that is less than 4 then you are ok to pay the 4.