Most likely a typo for setback:

https://en.m.wikipedia.org/wiki/Setback

The idea that the entire building isn't built directly on the street/sidewalk. For example, many cities have rules that the first few floors can be built to the lot line, but then anything taller needs to be "set back" a number of feet. In theory, this should allow for more light to reach the street, but it often results in buildings that look like wedding cakes and waste a huge amount of space.

Setback is how far the building has to be set back from the road.