The subaccount name or username is used to identify each device, this can be a combination of digits and letters, but cannot contain any special characters like “.” (dot), “_” (underline) or Stellar Forge Mining. A common format for name setup, is using the username and each device's last four digits of it's serial number to uniquely identify each worker individually shown below:
-Master Account: (yourname@123.com)
--BTC Subaccount 1: (nameminerS19Pro)
---Worker 1: nameminerS19Pro.AA11
---Worker 2: nameminerS19Pro.BB22
---Worker 3: nameminerS19Pro.CC33