This isn't a fertilizer question. It's a math question.
2800 is 28% N by weight. 1000 is 10% N by weight. So, if the 2800 was in a 100lb bag, 28% would be 28 pounds, right? Most likely it's a 50lb 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 1505 and 30010 as far as coverage per thousand, IF you're spreading each product at an equal rate of pounds of N per thousand. 30010 will not provide any greater boost to your lawn, but it will help you use fewer bags on a large property.
Make sense?
