the number of days per annum depends on your contract, but as per the qatar law should not be less than 21 days per year of service.

as far as i know, the leave days is not deducted from the total years of service in computing your gratuity.

you may have not worked during these leave days but it is a benefit given to an employee, and during your leave period you are an employee of the company and is assumed working during those leave days.