Should the 3 numbers on fertilizer equal 100?

Answer 1

No. The first number helps you figure out how much to spread over a thousand square feet of grass to add up to the one pound of "actual nitrogen" that one thousand square feet of grass needs.

Example:

You have a bag of 29-6-4. Divide 100 by 29 and you get about 3.5. This means you need to spread 3.5 pounds of this stuff for your grass to get the one pound of "actual nitrogen your grass wants during the growing season.