Control key in Maintenance order.

Hi Expert,

I have a doubt,

I have created one Work Center with control key PM02. Then I created a maintenance order with order type PM02.

but, when I check control key of operations in the mntc order, I found 1st operation alone has control key= PM01, remaining all are PM02.

Is it standard? If so could you please explain me the purpose behind that.

If there is any settings to avoid this, please tell me the configuration.

Thank you

Renjith.