@Siddharth Parna 

try this for your earlier question and subsequent question as well and give correct group sysId

var taskgr = new GlideRecord('sc_task');

// Replace 'GROUP_SYSID' with the actual sys_id of the assignment group you want to filter by
taskgr.addQuery('assignment_group', 'GROUP_SYSID');

taskgr.setLimit(5);
taskgr.query();

while (taskgr.next()) {
    if (taskgr.request_item) {
        gs.info('Task Number: ' + taskgr.number);

        var reqItem = new GlideRecord('sc_req_item');
        if (reqItem.get(taskgr.request_item)) {
            var shortDesc = reqItem.variables.short_description;
            if (shortDesc) {
                taskgr.u_short_description = shortDesc.toString();
                taskgr.update();
                gs.info('Updated Task: ' + taskgr.number);
            } else {
                gs.info('No Short Description: ' + taskgr.number);
            }
        }
    }
}

If my response helped please mark it correct and close the thread so that it benefits future readers.