DID Bulk Handler Q's

Hello, I am an old Nortel phone guy who is now a Network Admin working on implementing a FreePBX. I have a good understanding of telephony concepts but no bueno on the FreePBX implementation.
Regarding Bulk Handler>Inbound>DID - I am not understanding the required field descriptions, nor am I finding more granular documentation. Thank you very much for any and all direction and have a great day.
Required/recommended headers -

  1. description (description) - I think I’m good here.
  2. extension (Incoming DID) - this verbiage is confusing to me, but I am assuming this means “digits sent by carrier” (ie if the phone number is 517-555-1212 and the carrier is send 7 digits, this field should be “555-1212”).
  3. cidnum (Caller ID number) - I’m assuming this means the whole phone number “517-555-1212”
  4. destination (The context, extension, priority to go to when this DID is matched. Example: app-daynight,0,1),
    This one is the main reason for my post. Put the destination extension here, yes? (ie 1212). Can I just put
    the destination extension only? I don’t understand the example they give, for one, there is no extension number.
    5)6)7)8) fax_stuff. I’m assuming I can leave the fax stuff blank if I don’t need it.
    Thanks again for your time.

Create a single Inbound Route and then export it using bulk handler. There are tool tips there that describe the fields, and the wiki here: