Yup, just repeating what an E & I engineer mentioned once, in passing, he was only referring to the E & E bay.
Being an ex-Avionics man myself (744 and others), I started to count the number of rack-mounted electronic boxes in the 744 E&E bay. I couldn't find anywhere near 121 of these. When I started counting boxes and cards, the number easily exceeded 121. Again it comes back to definitions, I guess.