I happen to have the LNER Accounts for 1928 and the following information extracted from it may be of interest.
They had 90,741 mineral wagons, 30 were under 8 tons carrying capacity, 13,801 were 8 tons and under 10 tons, 18,703 were 10 tons and under 12 tons, 20,832 were 12 tons carrying capacity, 15,757 were over 12 tons and under 20 tons, 21,618 were 20 tons and over. Undoubtedly most of the 21,618 20 ton plus wagons were ex North Eastern 'double X' (e.g. slope sided wooden bodied wagons.). The steel hopper wagons were some years into the future.
For complereness the rest of the LNER wagon fleet consisted of 127,289 open wagons (other than mineral) , 30,746 Covered wagons. 3,324 Special wagons, 7,296 Cattle wagons, 14,116 Rail and timber trucks, and 4,547 brake vans.
If the 16,356 items of 'Service' rolling stock (not included above) , 2,879 were Ballast wagons, 68 were breakdiwn cranes, 11,103 were loco coal, ash and sand, 144 were gasholder trucks (gas lighting was still used in a few carriages, and for catering cars), 708 Mess and tool vans, 209 timber, rail and sleeper trucks, 222 travelling cranes, and 1,006 miscellaneous.
Ar the same time the LNER had 13,720 passenger carriages, and 7,295 non-passenger carriages (parcels, mail, perishables etc by passenger train)