Store Locator Plus Radius Behavior is set to “always use” in the base plugin. The Experience and/or Premier Add On packs extend the functionality beyond the basic “Always Use” setting. This setting impacts how the radius selector is employed and how locations are filtered before being displayed to the user.
The map search radius is set under the Settings /Search tab and the results after search is established under the Settings/Results tab with “Initial Search radius” and can be set to any number which equates to miles radius.
The radius selection options presented to the user in the drop down menu is set under the Settings / Search tab panel.