Depends on your bend angle.
Take bend angle and divide by two (2).
Obtain trigonometric tangent value for this result.
Multiply the value by the CL-CL distance.
The result is how much you have to advance or retract progressive offsets.
For example:
30? ? 2 = 15?
tan 15? = 0.268
0.268 ? 4" centers = 1.072"
Depending on which way the parallel offset has to sit, you would either add or subtract 1 1/32" from the bend mark measurement of the previous piece. Don't forget that this assumes your conduits start at points perpendicular (square) in the run. If they are uneven, you will have to add or subtract that difference accordingly.