Originally Posted by MaxFlyer

Here you go:

BA 874 LHR 13:30 → BUD 17:00
J2 C2 D0 R0 I0 Y9 B9 H0 K0 M0 L0 V0 N0 O0 Q0 S0 G0

So only 4 business class and 18 economy seats left. The different letters represent the different classes (business and economy in this case) and then sub fare buckets within each. J, C, D, R, I in this instance are business and the rest economy. Different fare buckets means different prices.