The Milestone system was added with the Season 7 Captainty patch, but some of them were not available to earn or make progress to until now. Unlocking Milestones will happen according to your playstyle, adding some depth to your choices.
The previously unavailable milestones for players and ships that have now been activated are ones for the number of Quest Board maps completed, discovering captained ships, selling provisions to The Hunter’s Call, ransacking and conquering sea forts, and making repairs to ships. All of these, except for the ship repair Milestone are for both ships and pirates.
This patch also corrects an issue that was causing the Skeletons Vanquished Milestone for both ships and pirates, to progress faster than intended. This patch also brings the totals back to the correct place for all affected. Some Milestones were also progressing faster than the intended rate when there were multiple crew members in the session, but this has now been fixed. There have also been some small exploits patched, including where people were burying and digging up a single piece of loot to achieve milestones.
Other issues fixed in this patch include fixes to the Captain's Logbook, letting you discard Captain's Voyages from the Captain's Bookshelf, and fixing the Captain's Logbook to show correct data when you start a new gameplay session and want to check your ship's history and days at sea.
Overall, this patch is almost entirely concerned with fixes and making some of the recently added features work correctly. They've also made some performance and stability adjustments in a continuing effort to make the game perform better across various machines. However, remaining in the list of known issues is reduced server performance while they continue working on it overall.