The credit for an efficient heat pump or air conditioner is 10% of the cost up to $300. The credit for an efficient gas furnace is 10% of the cost up to $150. So I’m not sure how you are showing $491. Although I think, there may be a separate credit for an efficient whole house circulating fan. To get the credit, you would have to break up the cost of the HVAC system into separate air conditioner and furnace components. So I don’t know exactly what you entered in the program.
You would need to look at form 5695. If using the online program, you can’t print specific forms until after you have paid, although you can pay and then go back to review your return and make changes before you actually file.