Please be aware that these are two different parameters. The offset angle of the arm is the angle between the straight line joining the arm pivot and the stylus tip and that parallel with the sides of the headshell or mounting point on the arm (this is why some arms are S shaped and others have the cartridge mounting points at an angle to the straight arm). In combination with stylus overhang, it helps reduce lateral tracking error and usually is set at around 23 degrees. This will be the same for any cartridge used with this particular arm as it is not a parameter of the cartridge, but the arm itself.

To set the offset angle correctly it is necessary just to make sure that the cartridge is mounted in the headshell straight and parallel with the headshell sides, as the angle has been taken care of by the arm manufacturer.

The VTA on the other hand is the angle between the record and the cantilever which is particular to each cartridge design, but is also around 23 degrees.

To set VTA, it is usually only necessary to adjust the arm height so that the arm is parallel to the surface of the record.