as you are going through the business section you should come to a page where you come to a page "Enter Business Income That's Not on 1099-NEC or a 1099-MISC/ there you'll find a line for returns and allowances.
Have you entered any Income for your Business? If you haven't, that may be why your screen is titled 'Let's enter the income for your test work' instead of 'Let's enter any additional income ..'.
If you enter some income by clicking the appropriate category and enter an amount, you should then get the correct screen.