There are lots of ratios. And...if you include custom ratios that any country elevator can make up for you, there are hundreds. A lot depends on the starting material and the percent of inerts in the starting materials. I am sure there is a computer program to calculate the possible ratios somewhere, (given certain base materials).
For instance I went to my supplier and asked for a special analysis ratio of 41-0-6.5...and eventually he agreed to make it and bag 4 tons for me.
Of course, 46-0-0 is the maximum urea ratio possible--you cannot get to 47 or 50-0-0 with urea. Likewise you cannot exceed 62 in a potash mixture as 0-0-62 is the maximum possible using potassium chloride.
For turf a high ratio of slow release is very important. However, opinions vary and some products are not suitable for certain grass types, soils or climates. There are regional laws, preferences and recommendations. Different seasonal ratios are often advised--and ratios exist to reduce disease or increase organic matter