Letter of Demand from Company to Settlement satisfaction

I had worked for my last company for 6.5 Years. I had enrolled to a Higher Education course on Jan 2020 through the company for which the company has to pay the Tuition fee in semester wise. The total amount entitled to claim for the course was Rs 218000. I had claimed Rs 168000 during the the first three semester of the course. But due to pandemic situation and Low salary , i had to leave the company and so resigned from the company dated 10 June 2021. Our batch of students had received an Email from the Higher Education team on 25 July 2021 with an attachment of Agreement letter which i had to print on stamp paper from notary and send back to company after signing on this. As per Agreement an employee have to refund the entire course amount of Rs 218000 in case of leaving the company before completing the course or leaving the company before 4 years after completing the course. But as i have already resigned and was serving notice, i had not signed any agreement bond with the company. Now The company has sent a Demand letter of almost Rs 286000 after adjusting my hold salary and other earnings in fnf Settlement. It has added Rs 318000 as recovery against Education Bond. How it has added 318000 instead of 218000 ? My financial situation and salary is not as good to bear this much amount. What are the legal aspect i can take in order to meet the liabilities as my experience letter is still pending with the company which i had to take and submit to my current organization. What are the approach, cost , risk and time i may have to bear in order to get rid of from this situation. Thanks and regards A private Organization Employee