IH: The sum of the balances on delinquent or derogatory installment accounts is too high.
An installment account is one with a fixed monthly payment for the life of the loan. Auto loans and student loans are common examples of installment loans. The total of the balances is high on your installment accounts with late payments or on which a lender has reported the account derogatory. Late payments are a proven indicator of risk. When credit line balances approach credit limits, risk is further increased because you don't have much credit available should it be needed, creating a greater chance of becoming overextended.
Paying bills on time every month is important to maintaining a good credit score. If you remain behind with any payments, bring them current as soon as possible, and then make future payments on time. Whenever possible, pay down balances on your accounts. Over time these actions will benefit your score.