Resetting Air tag

What is suppose to happen after item# 8?

It means your AirTag cover is secure in place and you can proceed to pair/set up your AirTag again.

To reiterate the eight steps in the document you have linked:

Here's how to reset your AirTag:

1. Press down on the polished stainless steel battery cover of your AirTag and rotate counterclockwise until the cover stops rotating.
2. Remove the cover and the battery.*
3. Replace the battery.
4. Press down on the battery until you hear a sound. This sound means that the battery is connected. 
5. When the sound finishes, repeat the process four more times, removing and replacing the battery, then pressing down on the battery until you hear a sound. You should hear a sound each time you press on the battery, for a total of five sounds. The fifth sound is different from the previous four. This indicates that the AirTag is now ready to pair.
6. Replace the cover by aligning the three tabs on the cover with the three slots on your AirTag.
7. Press down on the cover.
8. Rotate the cover clockwise until it stops rotating.