Adding line with @JamiePringle's suggestion to output chunking note

docs/examples/tutorial_parcels_structure.ipynb

@@ -406,7 +406,9 @@
     "\n",
     "In the first case, it is best to increase the first argument of `chunks` to 10 to 100 times the size of your initial particleset. In the second case, it is best to increase the second argument of `chunks` to 10 to 1000, depending a bit on the size of your initial particleset.\n",
     "\n",
-    "See also [the advanced output in zarr format tutorial](https://docs.oceanparcels.org/en/latest/examples/documentation_advanced_zarr.html) for more information on this. It is worth to optimise this parameter in your runs, as it can significantly speed up the writing of the output file and thus the runtime of `pset.execution()`.\n",
+    "In either case, it will generally be much more efficient if `chunks[0]*chunks[1]` is (much) greater than several thousand.\n",
+    "\n",
+    "See also [the advanced output in zarr format tutorial](https://docs.oceanparcels.org/en/latest/examples/documentation_advanced_zarr.html) for more information on this. The details will depend on the nature of the filesystem the data is being written to, so it is worth to optimise this parameter in your runs, as it can significantly speed up the writing of the output file and thus the runtime of `pset.execution()`.\n",
     "\n",
     "</div>"
    ]