Not sure if it is a joke, but it is possible, depending on your crediting rate. If you are using 30-year treasuries, or a very low crediting rate, when you accumulate at a low crediting rate, then discount at a higher PPA funding rate, your FT is often lower than your account balance. Depending on your demographics, and the interest rates being used, this can result in a maximum deductible that is lower than the sum of the account balances.