Step 2, copy the 18 digit you just entered with the keyboard.
Step 3, enter the space and click on my profile to modify the nickname.
Paste the numbers you copied in with the keyboard.
You must act quickly.
Paste with the keyboard for half a second, and click on the empty position next to it with the mouse.
This depends on the speed. If you can paste the complete copy you just copied, it means you have succeeded.
Click Save below.
If it's only half stuck, it's just your speed. Just practice a few more times.