Greetings - hopefully I can help explain it as I understand it.
The building limit is a hard cap on how many customers could potentially be in there at one time (per hour or something like that). And at this point, you cannot know this number before buying, and the devs are aware that this is not good for planning purposes.
The Traffic Index is about how much traffic passes the store on average - more traffic means more potential customers.
So, if you have high traffic, and low limit, customers might not be able to enter if you’re already at your building limit at that time, and you are losing business.
Having a maximized building limit won’t do any good, though, if you have really low traffic because you are paying for things, but don’t have a high volume of customers.
That makes perfect sense, and I figured it had to be like that. Would be nice to have a way to see the limit on the building prior to renting though so hopefully they will add that information when reviewing a lot.
Just to add a bit more info to traffic indexes: A building with a high traffic index requires less marketing to attract customers. However, a building with low traffic index, can reach the same amount of customers, if enough money is spent on marketing.
This is not very clear at the moment, due to marketing being very out of balance. That will be fixed later of course