Is the seller entitled to claim the extra 7% of the sold land area, and at what price—the selling price or the current price—if the buyer wishes to compensate him?

The excess area beyond the agreed-upon sold area remains the property of the seller (the heirs of the two mentioned individuals). They share in it according to their shares of the inheritance. They are entitled to sell it at its current market price or otherwise, or to relinquish it to the buyers, either gratuitously or for compensation.