I can clear things out why QuickBooks requires you to enter the same amount for those earning items, MelissaC.

You can only have one rate for all salary payroll items. The workaround is to delete the other item. Then, enter it as a commission or add it manually when you create a paycheck.

To set up a commission item:

1. In QuickBooks Desktop, click Lists, then  Payroll Item List.
2. At the bottom left of the Payroll Item List, click the Payroll Item drop-down button, and choose New.
3. Choose Custom Setup, then click Next.
4. In Payroll item type choose Wage. Click Next.
5. From the Wages list, choose Commission, then Next.
6. Enter the Item Name which prints on payroll checks and reports, then click Next.
7. Enter an Expense Account, then Next.
8. If you want to set a rate, in the Default Rate window, enter an amount or percentage to calculate this commission.
9. Click Finish.

Once done, you can then add the item to your employee's profile. Check out this article for more details: Set up commission payroll item and reports. 

Let me know if you have follow-up questions by leaving a comment below. I'm always right here to help ensure you're able to pay you employees.