No, leave is available only to those employees who have worked for the required number of days, i.e., 240 days in the preceding year. It is not like crediting the leave every 20 days or availing it after every 20 days of working. It is true that in respect of an employee who joins your establishment sometime between January and December, you can give a prorated number of leave provided the number of days he was present since his joining was 120 days (for 6 months), 60 days (for 3 months), as the case may be. But it is not counted for every 20 days, and hence it is to be dropped.