The leave rules for full and part time employees is the same as it will be covered by Factory Act / Shop & Establishment act and the relevant Standing Orders.
While the leaves are the same, the applicability will be in line with the number of hours they work.
So if he gets 1 day for every 20 days worked, in case of full time employee he gets a full day leave and the part timer gets leave of the hours he normally works. In effect, he also gets the full day as he was only required to work those many hours.