To edit a pre-defined rating, complete the following steps:
Right-click on the record you wish to edit and select Edit Record. A window similar to the following will appear:
Make rating changes in the Flow Rate Factor field.
Click to save the changes.
Click to exit Edit Mode.
Click to close the window and return to the grid.
Note: If you edit a rating, the change will only affect data from that point on (i.e. past data will not be affected) unless you run the "Recalc All" option (under System Tools).