It's hard to say how many circuits run through Cab1 without looking at our CSS Database, just as it's almost an impossibility to give an accurate capacity figure, without actually looking inside the Cab.
The reason being that the older 'threaded' system of connecting, that sees individual 'verticals' (verts) of 100pr cables would maybe house a total of four in a Cab of that size ..... whereby if the more modern Krone, Quante or the very latest push connection blocks were used, you could easily triple the Cab's capacity.
The smallest Exchange in the UK (as was back when I worked up in the Lake District), was Buttermere ... and it only had 20-odd 'subscribers' as they were then referred to working off it. That's 20 in total, not 20 in a Cab !!! Memory also recalls that a good few of those circuits were also a PABX system at the only hotel there was down the road.