Receiving settlement letters after absconding

Hi, I joined an MNC as an IT Manager and below is what drove me to abscond within 5 days of joining. I was being asked by multiple (senior) managers in the team to drive calls that involved coordination between multiple teams to the extent of getting what one team needs from the other to get a specific work done. At this stage I didn't even know who belonged to which team and what exactly was the problem statement that was being addressed. After interacting with one of the manager(who was at same level as mine) I found there is a complete contrast in the toolchain and ecosystem on which the solution was being built and what I had experience on. Even if I had continued, it would had left me with no personal space and I would have ended putting up way more hours than the normal work hours to match with the expectations. Until day 5 when I dropped the resignation mail, I didn't even have a company laptop to work with and was taking meetings on my personal laptop. I dropped and email to all the managers I knew that I am leaving as I won't be able to match the expectations and day 5 and asked to consider it as resignation. I didn't even had a laptop issued to me, no trainings, no dependency or no Knowledge transfer session was ever spent in me. I got a settlement mail to pay a huge sum as I have not served the notice period of 2 months. There was an employee agreement form attached to the offer letter which I was suppose to sign scan and send on 2nd day of joining and even that wasn't done as many things weren't clear. Is there is need for me to worry about this settlement letters. They in spite of me dropping mail to managers and later forwarding it to HRs paid me nearly 15days of salary. It would be great help if anyone could advice me on this situation. Thanks a lot