Unable to specify different grid columns settings for page and attachment
You can apply different Format to different Views Displays.
In your Attachment Display you have to click on the Format option, not on the Settings link. This will open the modal dialouge where you change the Format for the Attachment, but before you save make sure you change the For option to This attachment (override).

The default option for the For is &quot;All displays&quot; so if you change it under Attachment, it will automatically change on your Page Display as well, unless you override it like I described above.
Just remember that the overriding option appears on the modal dialogue where you're choosing the option, not on the &quot;Settings&quot; modal that depends on which option is set.