Partition should be done on total Ac. 8. The sharing of property will be as follows:
The property lying on the name of your Grand Father shall be divided into 5 parts i.e. Your father, Your three aunts, and your Grand Mother equally. i.e. 48 guntas each. Since your two aunts and GM had received more than their share, their excess share of 32 guntas (each) will be taken back and allotted to the other co-sharers.
Your mother will not get any property from your GF. She can only claim the share of your father. Hence, you Immediately file partition suit before the civil court and obtain injunction order not to alienate the property until the suit completes. You can contact me for further clarification through phone consultation.