This question could apply to stars orbiting a black hole, or planets orbiting a star, or moons orbiting a planet. The example numbers don't matter, just the concept.
Lets say that a star has a gravitational time dilation factor of 2 of the level of an observer on Earth (i.e. time runs twice as slow as an observer on earth.) At a certain altitude above the star the time dilation factor is 1.5. This should mean that anything at that altitude should also be running at that same time rate of 1.5. But a planet, which would have its own time dilation factor of 1.5 if it was out in distant space, is orbiting the star at that altitude.
So what is the total time dilation on the planet to the observer on earth? Is it 1.5 x 1.5 = 2.25? Or does the planet just retain its own factor of 1.5? Or something else?