Claiming outstanding remuneration after termination

I had been employed in a firm for 7 and a half months when one fine evening i received my termination letter via email. According to my knowledge its not a private limited company. I think it is a partnership firm. Now when I called the HR department they are trying to negotiate and settle me for 5 or 10 thousand rupees whereas I have months of payment pending. I told them that I want all that I have not yet been paid legally. So now I want to get your valuable legal advice as to know how much I'm legally entitled to. About the job and firm, it was business development role and in the job offer letter it's written Business Development Executive (trainee). It's also given that probation period will be 3 months and during the probation period there will be a particular target to achieve monthly. Now, the firm was going through a lot of problems and could not close any deal I had provided them. But they told me it is alright and everything would be made right soon. After about 5 months they terminated all employees except me in my branch. I told let me also leave but they insisted that I should stay and they would get everything right and the firm would make a new start. I was not getting salary but I trusted them and waited. They just gave me the office key and told me to wait. I just kept going to office, maintain it and marking my attendance. After about 2 months they hired some new employees, transferred the office key to the new admin and all of a sudden one fine evening, without discussing anything with me, they mailed me my termination letter! By now i had lost my faith in the firm doing business well. I now do not want to challenge my termination but i want to claim every single rupee I can, from all these months in which they made me a fool. This is the remuneration details. Technically speaking, I have not achieved the set target in any month of my employment. In my job offer letter, it is stated that for the 3 months of probation, the target will be so and so. Nothing is mentioned about after that. The only joining document i have is the signed job offer letter. I did not receive any appointment letter after joining. After 3 months I did not receive any intimation regarding extension of probation or termination. They did not tell me anything and I just continued working. The salary package is mentioned as: Basic salary - 20,000. T.A. - 5,000. H.R.A. - 5,000. Total - 30,000. Other clauses are: -- if the target is not achieved in the probationary period the company will be issuing a minimum salary. -- the company has the right to fix the minimum salary accordingly to the performance of the employee. -- if performance is not satisfactory minimum salary of 10,000 will be paid during the probationary period and company has right to terminate without notice. I have worked for a total of 7 and a half months. I have received only ?15,000 as salary till date. ?10,000 as salary for first month of probation and ?5,000 as partial salary for second month of probation. I have signed cash receipts for both. After 5 months from joining date, due to my continuous persistence to pay me something for TA and HRA they gave me a cheque for ?20,000 which I think is from the chairman's personal account. They did not take any receipt for the cheque. My question now is, how much outstanding remuneration am I entitled to receive legally now for the total 7.5 months of employment ? After the first 3 months, will I be legally seen still under probation or as confirmed for the rest 4.5 months ? What will be the terms after the first 3 months ? Can the company claim that the ?20,000 cheque was not for expenses but for salary ?