Answer
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In the Find dialog box in ArcMap, when you select one or more address candidates and right-click on the selection, one of the items on the context menu is Zoom to Candidate(s) and Flash. Clicking on this command changes the map display so that all of the candidates are displayed, and it flashes each of the candidates. If your map is zoomed out to a scale smaller than 1:50,000, then the map will zoom in to a scale of 1:50,000, assuming that all of the highlighted candidates will fit within the map display at this scale. If your map is zoomed in to a scale larger than 1:50,000, the map will only pan to the candidate locations, assuming that all of the highlighted candidates will fit within the map display at this scale.
The default scale of 1:50,000 is independent of the map’s coordinate system and of the coordinate system of the data that you are using and is not customizable.