I put some water in a cup and set the PH at 6.5 using down from up/down. I left it there for a few days to let it gas. I went to use it today and for some reason I decided to test the PH. To my surprise it has risen to 7.6. I thought maybe it was the instrument so I tested it with drops and sure enough the color was greenish rather than yellow. Note that I used both methods of testing when I set the PH to 6.5. Why would this happen?
As a side note, little bubbles had formed in the cup the day after I set the PH to 6.5.