He is eligible for earned leave for the period from January to June, and you have to give one day for every 20 days worked by him if he has completed 66.66% attendance. For example, if the number of workdays from January to June was 152 and he worked 110 days, then the calculation will be: 110 / 152% = 72.36. In this case, he will be eligible. However, if he worked for 90 days, then the calculation would be: 90 / 152% = 59.12, and in this situation, he will not be eligible. Now you can calculate as per the working days.
Regards, Zakir Hussain