Retrieving extension object fields definition

[andreapicaro]

Hi all,
I'm trying to retrieve structure definition of custom extension object with goal of handling them automatically.
Now my issue is the following:
The type of variable is Array of ExtensionObjects of type "Statistics" that is a custom type in the server

If I read value attribute I get a NodeID "ns=2;i=543217" for the data type.
From UaExpert, I've found the "Statistics" type definition that gives me the structure model I'm searching for but the nodeID to read it is "ns=2;i=543216"; not the same ID obtained from variable value, there is a -1 difference.

I'm struggling to understand what's the rule, how can I decide what node to read to get the type definition. Is there eventually some rule in OPC-UA to calculate nodeIDs of derived types (Array of Statistics in this case) that I'm not aware of?

Any hint would be appreciated

Thanks