Hi @Chiranjeevi K 

Please use below code and test it using background scripts. Probably, setLimit() would be the culprit as suggested by @Mark Roethof .

var currentUser = gs.getUserID();
var gr = new GlideRecord('incident');
gr.addQuery('caller_id='+currentUser);
gr.orderByDesc('sys_created_on');
gr.setLimit(5);
gr.query();
while(gr.next()){
gs.print('incident number: '+gr.number);
}

Thanks & Regards

Amit Verma