Sir Isaac Newton's Mistake(s)
It would have been the high tide under the moon that gave Sir Isaac Newton this impression of a falling apple 'drawing' the earth as it fell. From there, Sir Isaac developed a formula to explain the gravity of the universe. One that nominally specified one direction of fall was part of the cause of an opposite direction of fall.
The constant is the acceleration or weight of m caused by M at distance d from M. The magnitude of m is immaterial to the weight or free fall rate that M causes. (link).