Customer "Overdue invoices" amount balance

Hi,
I created several invoices amounting total $20,000. The client made a single transaction of amount $25,000 in my account against those invoices.That means I have received $5000 extra.
So, in Transaction (revenue) I added the amount received all at once.

But when I go to that customer, although it shows exact amount paid by them but it also shows me overdue amount. whereas it must have been cleared settled the balance after comparing the amount received and amount invoiced.
I am confused please elaborate whats going on in these calculations. Thanks
Is it Incorrect? or I am missing anything?