It is interesting to note that Mike did not need to fly Taree - Craven – Singleton to remain clear of Williamtown's Airspace, but if he flew a direct course between Taree and Singleton it would have brought them within 2 1/2 nm of it... not enough margin in case of an unknown wind blowing one-self off course into the zone.
If you look closely at the Craven/Singleton section of the Flight Plan you'll notice some unusual numbers. Whether Mike wrote this directly on the original FP sheet, or wrote it on another piece of paper on top of the Flight Plan – we will never know, but you'll note the 37 does compare to the 37 nm to run to Singleton, from Craven.
I believe this was part of his calculations to ensure he would avoid the Williamtown Airspace. The forecast wind was 240°T and using a protractor on the map would have given the track from Taree direct to Singleton as 239°T. Note the “1 + 6” on the Flight Plan - the “1” being a little ambiguous?
MDX pg 9