The 6 hour stat is just when it reaches 100% but, as I've learned from my phone just because it says 100% it might not truly be 100%. So it might take closer to 7 or so. I've never been awake at 5:00 or 6:00 am to check it right when it hits 100%.
I've read that phones and tablets will slow down charging when they get near 100% and kind of trickle charge the final 2% to 3%. So they bounce between 98% and 100%, charging and not charging so as to not over charge. But, the meter will still read 100% even when it's not truly 100%.
My phone has to sit @100% for 2 hours after to truly charge to 100% (ie when the phone says "I'm full" and shows the battery full icon notification) since I have an extended battery (ZeroLemon 7000mAh).