Penalty on Maintenance Charges

Hi, I have been living with my parent abroad for the past eight years. my parent have a rental property in Belapur (Mumbai, Maharashtra) which was vacated during the lockdown in 2020 the tenants used to pay the society maintenance and adjust it against the rent payment, right now the property is vacant and the maintenance dues are piling up, I contacted the society for settlement of outstanding dues and found out they are charging 21% PA interest on the total outstanding dues which is currently standing at almost Rs. 88,200/- as per the society as the tenant did not pay the maintenance dues for the last eight to ten months of his stay (another story)he interest charges are almost twice the annual maintenance charges which is currently 800 per month I have the society financial statement for 2018-19 which shows our total dues to be 1,800/- only and even if I calculate the maintenance based on current monthly charges it comes out to 48800/- from Jan 2019 to Jan 2024 which means the society is charging almost 40,000 in interest charges I am trying to get the break-up for the charges and the financial statement for the past four years but they are not giving my straight answer, I made a rough calculation on excel which shows currently they are charging more than 15,000/- annually in interest , is this legal? Year @800 PM Bal. End of Year Interest @ 21% Dec-19 9,600.00 9,600.00 2,016.00 11,616.00 Dec-20 9,600.00 21,216.00 4,455.36 25,671.36 Dec-21 9,600.00 35,271.36 7,406.99 42,678.35 Dec-22 9,600.00 52,278.35 10,978.45 63,256.80 Dec-23 9,600.00 72,856.80 15,299.93 88,156.73 48,000.00 Total Interest>>> 40,156.73