| Date | Value |
|---|---|
| Oct 17, 2019 15:38 | 430 ppm |
| Aug 26, 2019 16:36 | 400 ppm |
| Aug 5, 2019 15:53 | 390 ppm |
| Jun 25, 2019 16:04 | 420 ppm |
| Jun 11, 2019 15:55 | 420 ppm |
| May 27, 2019 15:50 | 420 ppm |
| May 13, 2019 15:39 | 425 ppm |
| May 6, 2019 11:44 | 375 ppm |
| Apr 15, 2019 12:01 | 400 ppm |
| Apr 8, 2019 12:50 | 410 ppm |
| Apr 1, 2019 19:48 | 420 ppm |