Most counters overhang by 1 1/2″, which is standard. This may be changed for whatever reason due to cabinet configuration, cabinet installation and/or personal tastes.
Can granite cantilever?
You can cantilever granite up to 12″ with sufficient support on the fixed end and with a large enough piece. Never cantilever unsupported granite where it might receive excessive stress like someone sitting on a counter or stepping on a counter to change a light bulb. You must have support underneath for these situations.