Ok let's break it down with the DPNS contract. First, here's the schema (i.e. the contract, what it's telling the network to write):
https://platform-explorer.com/dataContract/GWRSAVFMjXx8HpQFaNJMqBV7MBgMK4br5UESsB4S31Ec?tab=schema
If you go to Documents and go to the latest entry, here you'll see the data that this person is writing to the network. Notice that they're registering the username "Michael"
https://platform-explorer.com/document/AQ76mrKhkkVZkSNWrnPSQyMrMoZyc3iMVMkEvUsVuuPg