An ad can be shown in any place and at any moment within the app — such places are called placements. An exact placement is needed to distinguish the moments containing ads and to tracks the statistics (considering the logic of app usage).
We don’t know when and where to show the ads — so, in case the placements are not set up yet, the ads will be shown in “default placement”.
Additional ad management settings can be applied to a placement. E.g. you can set up different rewards for viewing rewarded videos. Moreover, you can turn the ads off completely, limit their timing, manage intervals between impressions and other settings (see the chart). Changes in placement settings are applied immediately — no need to update the app.