How to choose that very radius:
Assess the location of the customer company and its closest competitors, transport accessibility and the conditions it offers. Set the radius so that it appears on the map at the same time as the closest competitors.

Imagine your ideal user - who they are and how they get to the point. If most visitors travel by public transport, set the radius so as to capture transport interchanges.
Assess your options - availability of delivery or other conditions that can expand the display area.