Relation Between External Operations in Maintenance Order and PR

I have a Maintenance Order

there are 2 Operation External in Maintenance Order. usually it will create 2 item PR Service. but in my case it's create 3 PR item Service.

I look on the IW33(Display Maintenance Order).

Operation 10, becomes PR Service Item 10

Operation 20, becomes PR service item 30

and there is 1 another PR service item 20.

I see in the Tab Account Assignment. it's refer to the same order. but i don't know where is the Operation. the question is How to delete this Item when we don't know the Operation in Maintenance Order. or maybe how to know what is the Operation.?

Thanks.