I'm sure you do 47-50 hours duty per week, the point of the letter is you do signigicantly less flying than that. At least a third of your duty hours are likely to be sitting around Compass or CAT on industrially required long turnarounds earning allowances but not doing any work. Many of your colleagues seem unable to make that distinction. The pilots you mention are not only getting 3 to 4 days extra off per month but they are also flying more hours per month than you. In addition, many EF crews have a roster with several 'Available' days on which they can be non-opped, which means effectively being granted an additional day off.
The current Eurofleet agreement effectively strings out a small amount of work to fill a long period in order to get more cash, a not dissimilar practice to the Gate Gourment kitchen staff.