Hi janbu,
By converting the unwrapped phase into displacement either using the equation or the implemented method in SNAP, it should give you exactly the same answer.
By looking at the equation you posted, it seems that some parenthesis are missing so that you do not get the correct results. Hence, the equation should look like (unwr * 0.056 / (4*PI) ) and not (unwr * 0.056/4*PI).
We can test both equations by using a random value for the unwrapped phase and see what we get.
If we plug a random value (lets say 100) for unwrapped phase to the equation that parenthesis are missing, we get the following.
(100 * 0.056 / 4 * PI) = 4.3 but if we use the same value to the other equation with the parenthesis placed in place we have, (100 * 0.056 / (4 * PI) ) = 0.43.
As we can see, if we missed the parenthesis, then the values of our results are larger.
By the way, you can add a minus sign in the second part for the equation (-4*PI) so that values with minus sign indicate subsidence.
Please look at this post. Phase to Displacement Units?