Because the count ends when the ref reaches 10 and he did not...The ref picked it up late but Manny was always going to make it. Overall a poor and clearly bias reffing display..giving Manny much more time to recover, allowing him to hold but penalising Hussein as soon as he tried to do something about it and yes picking up the count clearly late...However that certainly does not mean Manny was "ko'd"..He got dropped, he got up and then he went on to pretty much control the rest of the fight.
If you don't include Torrecampo and Singsurat when he didn't get back up at all, then yes, 3 (and it really should be 2, because Barrera's should have been ruled a slip).
Not even close to being the best. But that was only his first trial fight at 126 lbs. He stood up immediately after he got KD too. Plus he dominated the whole fight, he KD the guy multiple times, and finished the fight, right after he got dropped. ASAP.