The chlorine is being used up disinfecting whatever is growing in your pool water (algae, bacteria, whatever). 0.6 FC is next to nothing anyways, and isn't enough to help your pool.
Shocking is a process. To shock, you add enough chlorine to bring the FC up to shock level, then you keep testing and adding chlorine to keep the pool at shock level until CC is below 0.5 and you can pass the overnight chlorine loss test. Initially you may need to test and add chlorine every hour. Later you may be able to test less frequently, depending on how quickly the FC level is dropping. Shocking can take a couple days or weeks or more depending on what condition your pool is in (barely cloudy versus green soup).
The process is laid out in Pool School.