Go back to the sticky and read up on the stability check part. It is characteristic of inexpensive meters that they aren't stable. It is also characteristic of users new to pH measurement that they don't always get things exactly right the first time out. So do follow the more detailed instructions of that sticky with respect to DI rinses, blotting, fresh buffers etc. If it is up to you to decide when to accept a calibration reading wait a good minute or 2 before accepting and at the completion of the cal, read one of the buffers several times over a period of an hour or so. Some fluctuation is to be expected. We hope that as you, and the meter, get broken in a little you'll get that down to less than 0.1.