to unlock the entire upper part of the chair: turn the lever anticlockwise towards the rear and let go; the upper part of the chair will now follow all your movements (= active dynamic seated posture).

This is all lower case. Can you fix that?
To unlock the entire upper part of the chair: Turn the lever anticlockwise towards the rear and let go; the upper part of the chair will now follow all your movements (= active dynamic seated posture).