Oakeley had many more than 15 floors - however, by the 1930's the work was confined to the underground floors, (with a couple of exceptions) so 15 would be a fair estimate of the number in use at that time. (For the record floors had been 1-16, C,DE,F,G,H,I,K,L,M,N,O,P,Q,R though R was only opened after WW2) Llechwedd is an equal possibility, it had 19 floors in total, but again not all in work (1-8 or 9, then A,B,C,D,E,F,G,H,I). Votty certainly had less (C-M at this period)
I think the photo of trackwork may be Oakeley, taken from Bonc Coedan, with the Middle Quarry Main floor and mills in the distance, the humpy mountain being Carreg Blaenllym - but it's difficult to tell for certain.
Graham
The map is the territory - especially in chain scale.