PO is taking base unit of measure instead of Order unit

Hello,

When I am creating a PO, its taking the Base unit of measure instead of the Order unit from the material master.

In the material master I have maintained the base unit as "EA" , order unit as "CS" and I have also set the Variable order unit as "1".

In the Purchase Info record , I have maintained the order unit as "CS" and Variable order unit as blank.

When I am creating the PO, it is automatically taking order unit as "EA" (base unit).

But I want it should automatically take "CS".

Please could you tell me why is it so.

Thanks.