Po and GR pice different

PO is created without material code and with cost center for 1 pc @ 10 rs/pc

now GR posted 1 pc price is material document is 10 rs

now again GR posted and then cancelled so the price coming in cancelled material document is 9 rs

can anyone sugesst for this system behaviour

can this be possible becuase of IV posted do that changes the GR price