| Date | Value |
|---|---|
| Mar 4, 2017 08:54 | 500 ppm |
| Feb 27, 2017 05:21 | 460 ppm |
| Feb 17, 2017 04:36 | 450 ppm |
| Feb 7, 2017 12:55 | 440 ppm |
| Feb 6, 2017 04:27 | 450 ppm |
| Feb 3, 2017 04:04 | 425 ppm |
| Jan 30, 2017 04:40 | 425 ppm |
| Jan 26, 2017 06:47 | 420 ppm |
| Jan 23, 2017 12:23 | 400 ppm |
| Jan 22, 2017 09:22 | 400 ppm |
| Jan 20, 2017 11:19 | 390 ppm |
| Jan 19, 2017 12:33 | 390 ppm |
| Jan 17, 2017 05:15 | 390 ppm |
| Jan 16, 2017 11:13 | 420 ppm |
| Jan 16, 2017 06:56 | 430 ppm |