My wife and I each received Letter 6419. The amount in box 1 for both of us is $2400. We received payments in our bank account for a total of $3200. What to do on return?

It appears we are missing payments in July and August for $800 each or a total of $1600 short on the payments. But, it appears I must enter $2400 and $2400 from Letter 6419 on our tax return.