This isn't a fertilizer question. It's a math question.
28-0-0 is 28% N by weight. 10-0-0 is 10% N by weight. So, if the 28-0-0 was in a 100-lb bag, 28% would be 28 pounds, right? Most likely it's a 50-lb bag if you're buying a professional product, so instead of 28 pounds, you have 14 pounds of N. One pound of N per 1000 sq ft would mean you'd be covering 14,000 sq ft. Half that rate would obviously go twice as far.
There is no difference between 15-0-5 and 30-0-10 as far as coverage per thousand, IF you're spreading each product at an equal rate of pounds of N per thousand. 30-0-10 will not provide any greater boost to your lawn, but it will help you use fewer bags on a large property.