Actually I selected the payment term in sales order as 

30% Advance End 30 Days

then I register the pay of 30%..

Then gain I paid remaining 70%... No special effect.. Normal effect like journal entries....

Then I create same sales order like 30% Advance End 30 Days

No i overrided and made the full payment instantly... No special effect(like alert) ..

So for what this payment terms is for.. please tell me clearly.. sorry if i made anything wrong...