double IR posting

Hi MM Guru's,

can you help me regarding the issue I encountered.

WE have a PO with qty 100. The GR qty is also 100.

But the user posted Invoice Receipt two times. 1 has qty 10 and 1 has qty 100.

Question,

1) did i miss any configuration that's why system allowed twice posting of IR(greater than GR qty)?

2.) the price of the the IR with 10 qty is equal to the IR of 100 qty, why is that? does system should auto compute the price with the 10 qty? then why it has been allowed to have a price with equal to 100 pcs? is this a config issue?

hoping for your help..

Thanks..