This is a document on how to adjust the Internal Carrier and Shipping Method code. This could be so that the method code can be fed back into another system for further processing, or just renaming for simplicity.
You’ll need to go to the Carrier that you’re wanting to change the expected Internal codes on.
Carriers–>Edit–>Advanced Settings panel
Once you’ve landed on this page, adjust the ‘Internal Shipping Code’ and ‘Internal Shipping Method Code’ as needed.
Once this is done, you will then have renamed your internal codes to the names you’d like.