Is it opened or closed or working? - Controlli S300 series actuator and valve

I have Gas fired boiler central heating system that has a Controlli S300 series actuator and valve.
I can not work ou if the valve is working or which postion is open on closed.
The bracket that connects the ble controlli actuator to the valve has an maker on it with two positions mark with the following:-
C --- a capital C on the side nearest the actuator
A --- a capital A on the side nearest the valve.
What do they mean?
I get the feeling the valve does not close. When the hot water is on only I can still feel the hot water above the central heating valve. Should this stay cold when the central heating is off?
How can I test this valve?
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