I follow the instructions .
1.Release the negative air pressure.
2.Attach the Cannondale high pressure pump and increase positive pressure until the shaft completely returns into the shock.
3.Follow steps 2 through 5 in the Setting Up Shock Sag procedure below.

Step 2.Release all the air pressure from the negative air chamber

3.See the Air Spring Pressure & Rebound Settings table above. Look up your total rider weight range (dressed to ride) to determine your air pressure settings for the positive and negative air chambers

4.Using the Cannondale high pressure pump supplied with your bicycle, set your air pressure in the positive air chamber.

5.Using the Cannondale high pressure pump, set your air pressure in the negative air chamber

Now when I do the number 5 is where the problem comes, when I put air in the negative chamber, the shaft start to expose itself.

Tried it many times, and don't seem to get it right.