These are what are commonly called ‘fare buckets’. As we all know, not everyone in a particular ‘cabin ‘ pays the same fare. ‘Special’, ‘Saver’, ‘Flex’ and ‘Flex+’ are easily recognised but even within these there are different fares as shown by the ‘fare buckets’. F and A are First class, J, C, I, O and P are Business and the rest are Economy.
The numbers behind the letters are the number the airline will sell in that bucket, but the maximum shown is 4 for First, 7 for Business and 9 for Economy buckets. And the numbers in a specific cabin are not additive, i.e. in your example the airline will sell 5 economy tickets, not 20. But they will sell them at the W ‘price’ (or above). Business is sold out, First has 2 tickets for sale (at the highest fare).