Answer
Slope interpretation: if the right humerus increases $1~mm$, it is expected that the right tibia will increase $1.390~mm$
The y-intercept has no meaning in this case, because there is no right humerus whose length is 0.
Work Step by Step
We could also have said that when the right humerus increases $1~mm$, the right tibia increases $1.390~mm$, on average.
