While there's no golden universal standard, these are some of the codes that you might find in your booking system:

Discount Economy: K, L, Q, V, W, U, T, X, N, O, S
Full Fare Economy: Y, B, M, H
Premium Economy: W, E
Discounted Business: D, I, Z
Full Fare Business: J, C, D
First: A, F

At StaffTraveler, we try to keep things simple, universal and understandable for everybody. That's why we don't use these confusing codes but easy-to-read classes. Please sum up all available Economy (ECO), Premium Economy (ECO+), Business Class (BUS) and First Class (FIRST) seats and enter the totals in the corresponding boxes in the StaffTraveler app.