The data points that are displayed on your screen (in the data point list in the top of your screen and in the status bar in the bottom of the screen when you move your mouse over the image) are displayed in a different format than the format that is used for copying data points or saving data points to text file.
When you define the axes of your graph, the number of significant digits for formatting your X and Y data is automatically calculated. You can change this by choosing Number of significant digits from the Format submenu of the Data menu. When the significant digits are calculated or set by the user, the formatting for screen and file or clipboard will be reset from the defaults, using the new significant digits.
The default format for new document windows can be changed from the Options menu. The format string needs to be specified using either \x or \X for the X coordinate, and \y or \Y for the Y coordinate. Use the upper case versions for fixed-length fields. Use the lower case versions for possibly shorter field widths. Both the X and Y coordinate must be present, in that order. You can use \t for tab, and \\ for a backslash.
The default format string for the screen is \x, \y, short fields for X and Y coordinates separated by a comma and a space. The default format string for file and clipboard is \X\t\Y, fixed field widths for X and Y coordinates separated by a tab character.
For each document window, you can change the format strings for screen and file or clipboard from the Format submenu of the Data menu. The format strings need to be specified in C-style printf format: two floating point arguments X and Y must be present. You can use \t for tab, and \\ for a backslash, and %% for a percent sign.
With 3 significant digits for X and 2 for Y, the default screen format becomes "%.3g, %.2g" and the default file and clipboard format becomes "%10.3g\t%9.2g".