The measured value implies that it is measured directly or indirectly, and not derived theoretically from other constants.

The value of G is correct up to four significant digits only, where as the value of electrostatic constant has been determined to a very great accuracy. Why? The value of G is not found to be consistent after that; ie, the 'measurement' does not give the same value for G.

I spoke about the G, the force constant, and not the force. Has the G for the force between two bodies, inside a space station or on the moon, measured at any time? I think there has not been any instance of such an experiment (I may be wrong). However, the G between bodies on earth has been measured, and has been found to be not consistent after four significant digits.