Genesis
6:19 And of every living thing of all flesh, two of every sort shalt thou bring into the ark, to keep them alive with thee; they shall be male and female.
6:20 Of fowls after their kind, and of cattle after their kind, of every creeping thing of the earth after his kind, two of every sort shall come unto thee, to keep them alive.
6:21 And take thou unto thee of all food that is eaten, and thou shalt gather it to thee; and it shall be for food for thee, and for them.
Then JUST SEVEN DAYS BEFORE THE FLOOD, God decides that he didn’t really mean two of each kind; he meant SEVEN of each clean kind. It is unlikely that Noah even knew what constituted a clean animal since that wasn’t determined until long after the boat floated.
7:1 And the LORD said unto Noah, Come thou and all thy house into the ark; for thee have I seen righteous before me in this generation.
7:2 Of every clean beast thou shalt take to thee by sevens, the male and his female: and of beasts that are not clean by two, the male and his female.
7:3 Of fowls also of the air by sevens, the male and the female; to keep seed alive upon the face of all the earth
7.4 .For yet seven days, and I will cause it to rain upon the earth forty days and forty nights; and every living substance that I have made will I destroy from off the face of the earth.
Summarizing for those of you who are shocked into disbelief, just SEVEN days left before the flood, God informs six hundred year old Noah that SEVEN times as many guests as Noah expected (thankfully only the clean ones however) will be coming to the party. Thus in seven days, Noah must change the whole configuration of the ship, gather enough food to feed seven times more guests than he expected and then go out and round up the guests – for this time God does not say that they will just “show up” at the boat.
The Church Of Truth™ 
GOD did not instruct Noah to do an animal sacrifice. Noah did that on his own. That is why GOD said “man is evil from his youth. And I shall put the fear of you (humankind) into MY animals. Man is responsible for putting a curse upon all mammal animals. But when the true Messiah arrives on earth that curse will be removed from ALL the animals. For no man will ever again kill any mammal be it animal or human. And ALL will eat the living food that grows on the trees and the food that grows from the soil.
Remember all the sacrificing is coming from the lying pen of the scribes who have tried to deceive all mankind that it is ok to kill animals and eat their flesh. They only ate flesh when they did a sacrifice and they did ALOT of sacrificing.
We are to be good shepherds and take care of all the animals. For they all belong to the GOD of Abraham Isaac and Jacob.
Mans Ego (self idolatry of himself) thinks everything belongs to him. When it does not. This is why when Messiah arrives he will rule with an iron fist against all those with said Ego
For Messiah the prince of peace will restore the Gan Eden (the garden of eden) back upon mankind. And all the animals will then become herbivores and they will again trust man. For mankind will will never again destroy any mammal life again. And man will attain what the GOD of Abraham desired in the first place Compassion Empathy and unconditional love
Shalom
The answer in Genesis 6 and Genesis 7-
1- The “clean” animals and birds= 7.
2- The “unclean” animals and birds= 2.
3- In Genesis 6:19= God said to take 2.
4- 4 verses later, God says to take extra clean animals (7).
5- The reason for this= more clean animals would be needed for sacrifice- once the flood was over.
An example: I tell you to get 2 cases of beer at the store.
I realize I/we need more= I call you, and tell you to get ______ more cases of beer, considering whatever the situation is.