Why is "two, four, six, seven, eight" sung in the song "Counting Ducks"?

There is a group of ducks passing downstream of the bridge in front of the gate. Come on, count them. Two, four, six, seven, eight, quack, quack, so many. I can’t count how many ducks I can’t count. How many ducks are chasing the ducks? The old man has a white beard. Sing and sing hometown operas and tell jokes. Children, children, hurry up and go to school. Don’t take a duck egg and take it home. Don’t take a duck egg and take it home. A group of ducks pass under the bridge in front of the door. Come on, come on, count them. Two, four, six, seven, eight, quack, quack, really. Oh, there are so many. I can’t count how many ducks I can’t count. I can’t count how many ducks are chasing ducks. The old man with a white beard sings and sings hometown operas and tells jokes. Children, children, hurry up and go to school. Don’t take a duck egg test. Take it home. Don’t test a duck egg test. Take it home. For the sake of rhyme, those lyricists can do anything. Maybe the ducks formed a formation of 2 2 2 1 1 when they swam past, so it is easier to count with two, four, six, seven and eight.