Unread folder count special options

I am on release 8.51. When I go to my embedded Outline properties to set up my unread marks, there used to be one choice under ‘Special’ and that was "Show folder unread information’. Now there are two…the original one and ‘Maintain folder unread information’. If you click ‘Maintain’ then I can click ‘Show’. I can’t find any documentation on ‘maintain’(…what would I want to ‘show’ unmaintained counts?) Anyone point me to where I can find some explanation? Or know from experience? I’d vote to click both. Looked in help, and both this forum and 6/7 forum.

TIA