Note: In SSRS report global parameters are added directly into to the report by right-clicking on the Parameters node and choosing Add. Microsoft dynamics adds several parameters into each report in order to pass data required every report to execute. Parameters created with query range or from contract classes are pretty straight forward but the other set of parameters, the global ones, are more difficult to understand. You can learn more about parameters from this link.
//Get the parameter value
boolean parameterValue = this.parmReportContract().parmRdlContract().getParameter("Parameter Name in SSRS Report").getValueTyped();
That is all you need to write to get global parameter value.