What Are The Side Effects Of Tylenol PM Or Member's Mark Acetaminophen?

I have been taking Tylenol PM or Member's Mark Acetaminophen PM every night for at least the last 2 years. Is this causing harm to my body and should I stop taking it completely. The Tylenol PM says you can take up to 8 capsules a day. The Member's Mark (same ingredients) says to only take 2 a day. What is the difference and is any amount safe? Thank you.