Hi Syman,
I found the solution in the domain model of the DatabaseConnector module. There it says: "After calling the statement, values in OUT or INOUT parameters are set and can be read."
So just take a look at the parameter which has the mode "OUTPUT" AFTER you have called your stored procedure. It then should hold the value returned by your stored procedure.
In case you are working with a list of parameters you need to cast the parameter to its correct type to make the "Value" attribute available, in your case its the "ParameterLong" object to which you need to cast your parameter to.
Hope this answer helps you, let me know if you need any iadditional help.