You can find the patchnotes to this hotfix tacked onto the main Parting of the Waves announcement, here: https://steamcommunity.com/app/552500/eventcomments/4365751613886817853/

As others said, the size of the patch is not added to the game, game will still only take up about 58gb of your disk.

But, indeed, we're not happy with the size of this hotfix or some of the patches we've had. We changed our patching structure during the Gifts of the Wolf Father update, to prevent an issue we had where every hotfix and patch would 'add' to the size of the game. Our new process now sometimes (but not always) results in patches being extremely big.

We're looking into the cause of the issue, somewhere in our building process, and we're doing our best to solve it so we can prevent further patches from being so heavy.