If that is just group formatting that is already built in. Go to the Online Today settings, first option is display, and set it to the second option which adds group formatting.
'ot_widget_title' => '{# [1:Member][?:Members] Online Today}',
The language string is ot_widget_title. Find that and edit as needed. IMPORTANT! Only edit the text, meaning the words member, members, and online today. Leave the rest alone as that language string is parsed based on the number of members - 1 member being singular, all other numbers given being plural. If you get rid of anything else there you will break things.
Not really - there are settings you can change though: