Primary Group , approximate average of 25-75% from American Pit Bull Terrier and/or American Staffordshire Terrier . The Secondary Group ,approximate average of 25-75% from Mastiff and/or Neapolitan Mastiff . A Tertiary Group (used in some programs) approximate average of 0-75%: American Bulldog , Boerboel , Bullmastiff , Bulldog Campeiro ,