If you make a payment against an invoice, the Account Summary at the bottom of this invoice does not change to reflect that payment.
This is the expected behavior in Core. The Account Summary does not include a payment if the payment date is after the invoice date. The values in the Account Summary are from the previous billing period, when the previous invoice was generated. In other words, the summary reflects the values of the previous payments made against that invoice, not the current one. So any payments made on the current invoice will reflect on the Account Summary of the invoices that are generated next.