You missed quoted the instructions but yes the assets must equal 5 times the difference. If your child was 18 or older than 3 times.
“Item Number 10. Total Value of Assets. In order to qualify based on the value of your assets, the total value of your assets must equal at least five times the difference between your total household income and the current Federal Poverty Guidelines for your household size. However, if you are a U.S. citizen and you are sponsoring your spouse or child age 18 years of age or older, the total value of your assets must only be equal to at least three times the difference. If the intending immigrant is a foreign national orphan who will be adopted in the United States after he or she acquires legal permanent residence, and who will, as a result, acquire citizenship under section 320 of the INA, the total value of your assets need only equal the difference.”