Dear, anything paying above the minimum wages of particular states, a company can include anything in your CTC. Currently, a call centre including coffee and drinking water used by the employees are taken into CTC. It is not a violation, but you will get it after completion of five years continuously working at the same company. In case you leave the job before completion of 5 years, then you would not receive gratuity. You can consider this amount as separate from your side. Don't take this amount into consideration. You will get 15 days' wages per year of your current salary (if you have completed 5 years).
Suppose your basic salary is 30,000/month, and you resign after completing 6 years in the same company, then you will get: 30,000/26*15 = 17,307 for 1 year, but you worked for 6 years, so you will get 103,846.
Regarding your maternity: there is no link between maternity and gratuity. If you worked in an organization for a minimum of 80 days, then you are eligible to receive maternity leave for 12 weeks.
Best Regards,
Sajid Ansari - Delhi