It is the total amount invested by you in all coins that you currently hold.
For example, on 1st March 2021, you invested INR 100. This is your investment. One month later, on 1st April 2021, this INR 100 value became INR 500 on account of the markets going up. Now, on 1st April 2021, you took out INR 250 from your investment of INR 500. In other words, you sell half of your investment’s current value. Now the current value becomes INR 250. Since the current value is the sum of current investment and current returns, they reduce by half of the previous value as well. Therefore, the current investment which is the fund that is currently invested becomes INR 50. Similarly, current returns become INR 200 from what was previously INR 400.