"Delta138" seems to be a keyword or code of some sort, but without context, it's difficult to provide a specific description. It could potentially refer to a flight number, a product model, a project name, or any other identifier depending on the domain it's used in. https://www.evernote.com/shard/s413/sh/388a7969-3c9b-3903-69b0-c87e98470b9d/qrl1934dhaiTS1kjhHEtmAnasJITyCyfbT975kVzkzUu8WSPiide38CKhw