As per the title - what does this mean 'Not judged on the Group System' mean on a show schedule

It means that there will not be a contest for all the BOB in each group and all BOBs will go straight into the Best in Show contest.

In the group system all Hounds, Terriers, Toys, Working, Pastoral, Gundog and Utility will have a group contest when all the BOB from each group, will meet and the best will be chosen. These group winners will then go forward to the BIS so there are only 7 dogs present. In a not judged on group system every Best of Breed will go into BIS.

Thank you - entered my pup for his 1st show and give him a run out before his first champ show

Good luck, hope you enjoy, the same applies to the Best Puppy in Breed, should you win that and I hope you do then you go straight into the Best in show ring there will be no group.