Data inaccuracy: Google Maps relies on data from a variety of sources, including user-submitted data, satellite imagery, and third-party data providers. It is possible that there is an error in the data that Google Maps is using to generate its roundabout exit information.

Algorithmic error: Google Maps uses algorithms to process and interpret the data that it receives. It is possible that there is a bug in the algorithm that is causing it to incorrectly count the number of roundabout exits.

Map rendering: Google Maps generates maps dynamically based on the user's zoom level and other factors. It is possible that there is an error in the way that Google Maps is rendering roundabout exits at certain zoom levels.

Why does Google Maps incorrectly indicate roundabout exits by subtracting one exit?