Easier to just remeber there is 3 lbs of N in gallon of 28% at 10.64.

                                                  3.3 lbs of N in 30% at 11

                                                 3.6 lbs of N in 32% at 11.4

If you put on 50 gallon an acre, thats 15 units difference, like $9-10 an acre.   thats only 10% off target, but no biggie though eh?