HI, I have a Beretta and the notches on the chokes are as follows ... 1 - Full choke , 2 - Improved modified, 3 - Modified, 4 - improved cylinder, 5 - Cylinder.
1 would be, on mine, the tightest choke ie less spread and a tighter pattern
5, as a cylinder would have no choke therefor a wider pattern.
As said by the Verminater, it depends on the range you are shooting, but I would try changing to a more open choke and give it a go.
I would use my local library and read up a little on various types of shotgun shooting, it could clear things up a lttle for you.
Good Lu