Warning in PO: Can delivery date be met?

i experts,I am in Enterprise version and I have an annoying problem that would like to ask you about.When creating a PO and setting the delivery date for less than a week from today: Can delivery date be met? Message ME040.I looked for a parameter for this and couldnt find it, so I ended up disabling the message.Is there any other more polite way of dealing with this situation, I always get the Warning

Hi,This is the some sort of warning/information message popped up by SAP to check if you are sure that your required delivery date can be met by the vendor. The reason for such message existence was due to the setting in your planned delivery time in the material master. Therefore, one of the alternative solution is to redefine your planned delivery time.Cheers,HT

backward scheduleing逆向排程客户要求到达日期-运输在途期-运输准备期-装载时间-包装/拣配时间=交货日期（delivery date）一般情况下运输准备期与装载时间是平行同步计算的，因为在装载的时候就可以开始联系运输提供商。

It is harcoded...Thanks a lot.Fernando.