Difference between price release from CK40n and CKMLCP

Dear Experts,

We have material ledger active for all plant, As per our practice we release material price from CKMLCP and marked standard price as future price at 1st day of the month through CK40n, In last two period we also release price from CK40n because of this system generate two price changed document one for CKMLCP and another for CK40n.

1, My question is why system create two document.

2. If we release price from CKMLPCP as standard price for the next month it is necessary to mark price through CK40n

3. If we don't mark price from CK40n and only release price from CKMLCP, what would be the impact.

Thanks & Best Regards,