The base58 number
16w4zZWjWnhfEasJcSbfDQeHJRk1LytPHF5ir1ZS9mtUD5adsdH is a base58Check encoding of the (compressed) public key:
which corresponds to
KwY7eRvXXFd7HPX4Zuv8STZMLsVSe2X22HkU24Av84W1Cb7Rd5Yh, and whose address is
16reZXagkyToongduimD25SEerXwP3MQ4n. Note that your private key is actually a bit more than a private key. It is a 38 bytes number which is a base58Check encoding of a number which contains
34 bytes (rather than just 32 for a secret key). There is an additional version byte
0x80 at the beginning which indicates that the private key is to be used for the main bitcoin network (rather than a testing network). There is an additional
0x01 suffix byte at the end (just before the 4 checksum bytes) which indicate that the public key associated with this private key is to be generated in compressed form (33 bytes) rather than uncompressed form (65 bytes). So while it is true that your WIF representation of your secret key leads to a unique address (one corresponding to a compressed key on the main network), the actual 32 bytes secret, can potentially lead to 4 addresses (depending on compression status of the public key and type of network).