Who will pay the bill

In eighteen century there was a restaurant, and on the roof wall there was a signboard and something interesting was written on it , it was : "Eat as greatly as you duff and put aside your grandchildren produce the bill". A vagrant entered the cafeteria, ate as highly as he skeeter , after eating the lunch the man put tooth stick and start watching movie in cafeteria , the man was very happy that he would not pay the bill as they would charge his grand children in future  the servant gave the bill he perspicacious to the unusual, "Don't you look at your sign board, come with me i will show you, my offshoot needs to grant for this bill". The waiter didn't get surprised he smiled and said , "Sir, this is moan your bill. This is your grandfather's bill who ate many years ago".