Ok you are more than likely correct since I don't know the numbers of the nitrogen content.
Yet Based on the bag shown online they gave you the correct square footage for I pound of N. So we can assume that your bag is correct as well.
I see you did your math based on the label on the bag
Be careful a lot of different bags of ( for example 22-0-11 ) May say they cover different square feet. One company may say its 22-0-11 covers 12000 square feet. While the other company of 22-0-11 may say it covers up to 24,000 sq ft. In such a situation your calculations will result in different amounts of nitrogen.
Many companies do this for marketing purposes. Which would a novice pick up? A bag that covers 12,000 or a bag that covers 24,000. They are the same fertilizer but one of them, if you use your calculations,is being put down at half rate.
Often better to do calculations based on Nitrogen content. So that these marketing ploys don't fool us.
I digress
You probably already know all of this I'm just giving out the information for others who read the thread.
The lawn care nut does excellent videos of the calculations I just can't figure out how to copy and post the link from my iPad.