| Value | Category | 
                                    
                    
                        | -999 | -999 | 
                                    
                    
                        | -888 | -888 | 
                                    
                    
                        | 1 | May | 
                                    
                    
                        | 2 | June | 
                                    
                    
                        | 3 | July | 
                                    
                    
                        | 4 | August | 
                                    
                    
                        | 5 | September | 
                                    
                    
                        | 6 | October | 
                                    
                    
                        | 7 | November | 
                                    
                    
                        | 8 | December | 
                                    
                    
                        | 9 | Did not receive | 
                                    
                    
                        | Sysmiss |  | 
                            
            Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.