Network SSID of portable Wi-Fi hotspot is incorrect. Why?
When you do the initial set up of Wi-Fi hotspot, SSID is the last 4 digits of your phone number.
1. SSID is shown as 'Model _last 4 digits (of your phone number)' during the initial booting.
How to setup
If you have different SSID, that is because you do initial boot without inserting SIM card.
This is normal behavior and you are able to change SSID number through setting.
Settings > Tethering & networks > Wi-Fi hotspot
Set up Wi-Fi hotspot