Wish had remembered where that free GIS tool was, but alas. Lets eyeball and do some math.
The communities of Richmond, Garrison Woods, Altadore, and South Calgary, which generously could be called Marda Loop add up to:
Richmond 5,250
Altadore 7,290
Garrison Woods 2,860
South Calgary 4,540
19,940. For comparison, the entire beltline is 25,880.
If we do this instead:
we end up with roughly:
9276
with east of crowchild only being 6,729
and thats if you can get a service to the middle of marda loop.
if you explore a bit on the census, around 40% of that catchment can work from home, which degrades transit demand, and around 20% of the population took transit to work in 2016 (more walked or biked than took transit), pre-work from home.