| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 7 | 
                                    
                                    2.6%
                                 | 
| 0 | Less than 1 hour | 120 | 
                                    
                                    44.4%
                                 | 
| 1 | 26 | 
                                    
                                    9.6%
                                 | |
| 2 | 36 | 
                                    
                                    13.3%
                                 | |
| 3 | 12 | 
                                    
                                    4.4%
                                 | |
| 4 | 12 | 
                                    
                                    4.4%
                                 | |
| 5 | 15 | 
                                    
                                    5.6%
                                 | |
| 6 | 2 | 
                                    
                                    0.7%
                                 | |
| 7 | 2 | 
                                    
                                    0.7%
                                 | |
| 8 | 3 | 
                                    
                                    1.1%
                                 | |
| 9 | 1 | 
                                    
                                    0.4%
                                 | |
| 10 | 5 | 
                                    
                                    1.9%
                                 | |
| 12 | 3 | 
                                    
                                    1.1%
                                 | |
| 16 | 1 | 
                                    
                                    0.4%
                                 | |
| 18 | 1 | 
                                    
                                    0.4%
                                 | |
| 20 | 2 | 
                                    
                                    0.7%
                                 | |
| 24 | 6 | 
                                    
                                    2.2%
                                 | |
| 25 | 1 | 
                                    
                                    0.4%
                                 | |
| 28 | 1 | 
                                    
                                    0.4%
                                 | |
| 30 | 3 | 
                                    
                                    1.1%
                                 | |
| 36 | 1 | 
                                    
                                    0.4%
                                 | |
| 40 | 1 | 
                                    
                                    0.4%
                                 | |
| 43 | 1 | 
                                    
                                    0.4%
                                 | |
| 48 | 2 | 
                                    
                                    0.7%
                                 | |
| 60 | 1 | 
                                    
                                    0.4%
                                 | |
| 72 | 2 | 
                                    
                                    0.7%
                                 | |
| 84 | 1 | 
                                    
                                    0.4%
                                 | |
| 168 | 1 | 
                                    
                                    0.4%
                                 | |
| 720 | 1 | 
                                    
                                    0.4%
                                 | |
| Sysmiss | 1146 |