Query Regarding Assign Planning Plant to Plant

Hello,

I was practicing PM configuration and stuck with assigning planning plant to the plant. Through spro and assign path, when I go to the assigning page get this message (picture). But there is no such planning plat that message asking for. My created planning plant is not the one message showing.

Would you please describe the reason for such message. For your information, I am new at PM Module.

Regards,

Ashkul Milton