Google Play Families Policy
Google has introduced a Families Policy which requires you to submit information about whether or not your app is targeted towards users under 18. All apps on Google Play need this section of the submission completed.
When submitting an app on your behalf, we usually select a target audience of over 18, and mark the app may unintentionally appeal to children. As the requirements for targeting younger audiences include policies on how data is handled, ad networks etc, we're unable to make those assurances on your behalf - and submit with this selected. This may lead to 'not designed for children' showing in the app store - but it is a separate setting to the 'age rating' displayed, which still remains at 3+ for the majority of stations.
If you wish to target a younger/broader age group, you can submit to Google an updated target audience at any point. This can be done by logging in to your Google Play Developer Console, selecting the app, Store Presence, App Content. Google will review this and email if there is an issue.