Those fields refer to receiver indentifiers.
Is this going to be an inbound transaction to you? If it is, this information is how you identify your company
EDI-wise to your trading partner. Someplace in your EDI software you define your company identifier and qualifier and that's where it's pulled from. For us, at our company, we went like a lot of other companies and specify "01" in ISA07 and our company's DUN's number in ISA08 as well as GS03. However, with our distributor, we use "ZZ" and the number the distributor assigned to us in ISA08 and GS03. It all depends on what you can work out with your trading partner.
If it's an outbound transaction to you, this information will identify your trading partner, FedEx, and they should supply you with that information.