The basic setting of the ignition is something you have to do to get the engine to run in its basic setting, which is needed to get the engine running at all, especially if the distributor has been removed, for example because the cylinder head had to be lowered.
1st Turn the removed distributor to its basic position and make sure that it is not accidentally twisted during installation.
It is important that the marking on the right side corresponds to the picture here and on the left side also the marking (not to be confused with the rivet which is also inside there).
2nd Turn the motor on the pulley until the mark on the other mark is exactly in the window.
This approached line is the edge from the manufacture of the manifold.
In reality, this is what it looks like:
The marking shows the "hole" on the rotating part (swing or transducer) has a marking which must be the same as the marking on the fixed part.
Simply bring this "edge" into line with the equivalent edge on the cylinder head. Make sure that the distributor is not twisted.
And so you can start the engine, it must work. If not, there is another error.