Possible Clues:

• Mark McGwire stat: Abbr.
• They fill up the day: Abbr.
• 168ths of a wk.
• Some baseball scores: Abbr
• 'Another 48 ___'
• Parts of a day, briefly
• Slugger's scores: Abbr
• Billing units: Abbr.
• 9 a.m. and 5 p.m.
• They're either a.m. or p.m.