duplicate invoice, partial payment, residual payment

Hi every body

I am facing some problems in AP

1. I post a invoice in AP

I see that there are two document number 190000006

Please tell me why?

2. I pay a invoice with amount of 200000 in two times

firstly, I post a partial payment with amount 100000 (document number 1500000032)

secondly, I post a residual payment with remaining amount 100000 (document number 1500000033)

The invoice is paid completely and clear automatically but the are two documents (1500000032, 1500000033) is not cleared

Please tell me the payment process? how to clear payment document?

Thank in advance

Minh