Some of the listed codes are similar to the ones I was familiar with as a past CO non-revver. These are strictly guesses, but here goes:

I'm guessing that PSUP might mean something like positive space, upgradeable. In the general non-revving world, postive-space bookings remove a seat from available-to-sell inventory, and are typicaly used by employees travelling on company business (this can include cabin staff flying to a city where they will start to work a flight). These kinds of PS bookings generally can be upgraded once all eligible revenue pax have been upgraded.

S3 might be the general classification for employees traveling on leisure, using their pass privileges. Since boarding is usually in order of seniority, the chronological date order lends some credence to this guess.

S3C might be a companion pass/buddy pass rider who is being escorted on the flight by the employee who provided the pass (in this case, the buddy assumes the boarding priority of the employee providing the pass).

S4 might be a pass-eligible pass rider who is NOT the employee and is NOT travelling with the employee - that is, a spouse, parent or dependent child of an active employee.

Again, these are strictly guesses as I have no direct insight into DL's policies, but still.....