those numbers refer to the specific gravity of the product, or weight. Higher numbers tell you that a cup of the sauce would way more than a cup of the lower number sauce, so in essence higher numbers mean a thicker tomato product. The thicker your sauce the less of a fresh flavor, and the more of a rich flavor it will have. As a rule of thumb, I tend to go for thicker sauces as the oven temps go higher. This is because slower baked pizzas have more time for the water to evaporate out of the sauce. You may find it interesting that neapolitan pizzerias tend to use a very thin sauce even though they are baking at ultra high temperatures. Their goal is a very fresh tasting product no matter what, even at the expense of it being somewhat soupy. On the other side a typical american delivery pizza uses a sauce that is very thick, almost to the consistency of a paste. This allows you to put lots of sauce on the pizza and still have it hold up and not be soggy when it gets to the customer a half hour after being made. You may want to experiment with using a thinner sauce and putting it on the pizza after the cheese goes down. This is another way to get away with using a thinner sauce without a soggy crust.