Regulating a shot gun is purely about specifics.
To shoot a predetermined percentage pattern at a set distance with particular cartridge .
EG. To shoot 70% within a 30" circle at 40 yards using a fibre wadded Winchester "Game" No 6 shot .
The gun will be fired several times and then have the chokes opened if the pattern is too tight . It is a matter of trial and patience that can take time , but with modern cartridges being very consistent most guns with standard bored chokes will shoot reasonable patterns . It is the older guns that may need to have choke cones as well as choke bored to give you what you want
Regulating a shotgun is not about where the gun shoots no matter what any one else tells you , that is down to the user to learn and take into account when calculating lead .