The sentence you quote only asserts that an equation that is part of a scientific theory yields a certain numerical result if appropriate numbers are supplied for the mass of the sun and the mass of the earth etc The calculated numerical value is significant because for one thing  watts of energy is the equivalent of one of the larger incandescent light bulbs used in homes They are easy to see from a few hundred meters away but from even someplace as close as the moon it would be a very faint signal A gravitational wave that would cross space from the vicinity of another star diminished by the r squared rule and still be powerful enough to agitate our crude instruments would have to be a very major event