​Confusion About New Birth

John 3:4-12 
 
4  Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother's womb, and be born? 
5  Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God. 
6  That which is born of the flesh is flesh; and that which is born of the Spirit is spirit. 
7  Marvel not that I said unto thee, Ye must be born again. 
8  The wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh, and whither it goeth: so is every one that is born of the Spirit. 
9  Nicodemus answered and said unto him, How can these things be? 
10  Jesus answered and said unto him, Art thou a master of Israel, and knowest not these things? 
11  Verily, verily, I say unto thee, We speak that we do know, and testify that we have seen; and ye receive not our witness. 
12  If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things?