Thanks for the reply,
We are not greedy, my mom asked them get it written that we are taking 10 lakhs from property value, and in future to consider the future value of 10 lakhs, but they made my mom to sign the release deed. As my mom was not in a postion to tackle situation, as she needed to take care of us she signed it on our behalf as well.
She was not in a position to get to know the exact value of properity as well when she had signed.
Ps edit: the deed was signed in 2014 not 2011 and they verbally said that 10 lakhs is the value currently in 2014.