CTC is drawn to get an idea about the cost to the company. However, when the salary deduction in lieu of leave is calculated, it is always based on the monthly salary before the deduction of PF/ESIC/PT, etc.
For example, if a person's CTC is 1L/A and the monthly gross salary is Rs. 6000, then the salary for 1 day is calculated based on 6000 divided by the number of days in the month. Subsequently, the rest is calculated based on this 1-day salary.
When granting leave for 4 days, as Roshani mentioned, it is entirely based on the company's policy.
If you have any further queries, feel free to ask.
Regards,
Pranali G