Symbols for Edited Values
The value column in the grid view, or the value in the legend of the plot view may include any of an exclamation mark (!), a question mark (?) or a notebook icon. Here's an example from the grid view showing all three:
The question mark indicates that the Questionable Data flag was set at the time the value was recorded. This does not mean that there is anything wrong with the value, only that the flag was set.
An exclamation mark beside a notebook symbol indicates that someone used the Data Editing feature to set this value manually. A note is always created when a value is edited to record when it was changed, what it was changed from, and who changed it. The ability to edit values to correct errors or to add values that were measured manually is an advanced feature, protected by a security privilege.
It is also possible to add notes without changing the value, in which case there will be a notebook symbol without an exclamation mark. You must have the Edit Data privilege to create these notes, but you do not need any extra privileges to click the notebook symbol and read those notes. Operators who do not have the Edit Data privilege can still create notes
An exclamation mark without a notebook symbol indicates that the Manual Data property of this tag is set.