A2. Was there anything colored under the chart when you measured? The inaccuracy may have been caused by things such as the desk that the chart was placed on.
When you measure, place a white material such as a board or paper underneath the chart.
If you use a board, use the backup board that was supplied with the colorimeter.
If you use paper, use a stack of at least 10 sheets of the same paper that was used to print the chart.
For details, refer to Calibrate and Executing Controller Calibration with Color Centro.