Actual land is more than what in the document.

you can file suit for declaration ,if no objection is filed by anyperson then the land will get mutated in your title.

The documents will show that you own 50 cents. If you wish to be able to sell what you actually possess or occupy then you have to get an official survey doen to verify that the land belongs to you.

If the land has been bought by someone earlier in your family, then the earlier documents will show the correct number somewhere and that will help you get it in your name.

If all the earlier records show that it was always 50 cents, then it is difficult to get the records changed. However, when you sell it to someone, you can actually measure the land and put the measured value in the agreement. This may help the future owners to modify the records in case what you say is true.

However, it is difficult to have such a mistake to remain for long as the way land is measured in India there are countercheckc which prevent such mistakes from continuing even though the mistakes may occur sometimes.

S Jadhav