SHVC,
The difference is as follows:
A) Two roster periods per finical year can be reduced to 9 days off, But you still get minimum 132 days of per calendar year.
B) You can be rostered up to 8 Available days per finical year. These day still come out of your total work days so your not doing any more work just being rostered differently.
For these two things you get paid an additional $5.78 per duty hour.