If you measured by volume this would explain it.
On a slightly different topic, I've found that the type of salt used determines how thick the brine eventually gets. I had preserved some lemons with table-grind sea salt and the brine got very thick indeed. I made another batch using coarse sea salt and the brine still got thick, but not nearly as thick as the batch made with table-grind salt.
I wonder why this is?
Because of gaps left between the granules of coarsely ground salt, it will contain less weight of salt than the same sized container of finely ground salt. Less weight = less dense brine.
Another very good reason for moving to weighing with scales rather than measuring with cups.
I did indeed measure by volume, so your explanation is spot-on. Thanks.
But now I am wondering why salt makes the brine thick at all....