improve comments

2-Regression/1-Tools/notebook.ipynb

@@ -362,14 +362,14 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Note that there is one green dot for every black one, on the X axis. The value on the Y axis is the machine's prediction (i.e. on the line), based on bmi alone"
+    "Note that there is one green dot for every black one, on the X axis. The value on the Y axis for the green dots and the line is the machine's prediction, based on bmi alone. The black dots are the _actual_ values, for the same bmi."
    ]
   },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Presumably the point of test data is to see if the prediction matches the reality, but we didn't analyse that here"
+    "Presumably the point of test data is to see if the prediction matches the reality, but we didn't analyse that here. I guess we would see how far off each green dot (prediction) is from the equivalent black dot (reality)"
    ]
   },
   {