Dear Biswal,
Suppose in a calendar year, a particular employee was not laid off and did not avail any maternity leave or EL, the entire 365 days of the year, including the weekly and other holidays, days of CL and/or SL availed by him, should be taken into account for the purpose of calculation of his EL earned in that year. Then the EL earned by him would be 365/20 = 18.25 or 18 days.
In case that employee was on maternity leave for 182 days, her number of days present becomes only 183 and falls below the threshold of 240 days. However, if the ML is added to the 183 days, she notionally crosses the threshold and becomes eligible for computation purposes. Yet, she will not actually earn any EL on the 182 days of ML; hence, her EL earned during the calendar year would be 183/20 = 9.15 or 9 days only.
In another case, if the employee goes on 20 days EL earned in the previous years, the number of days present becomes 345 days, and in that situation, the EL earned by him would be 345/20 = 17.25 or 17 days only.
It is to be noted that in both cases, the days of absence availed by way of weekly off, national and festival holidays, and CL have been taken into account for both the purpose of computation of 240 days of service as well as the calculation of leave earned.
Hope I have cleared your doubts.