The 57 on the Heinz Ketchup bottles doesn't really have much meaning other than it being a lucky number according to the founder of Heinz ketchup.
Henry Heinz considered the number 57 to be a lucky number so he had it put on the Heinz Ketchup and it just stuck over the years.
Heinz other products such as Heinz 57 Sauce that is used for chicken, Pork and steak also has the number 57 on the bottle and it's just because they left the number 57 on the bottles.
That is because Henry Heinz wanted to put it on their and they just decided to leave the lucky number 57 on the Heinz products.