add comment and signal vs. coordinates to the third example

base_classes/NXdata.nxdl.xml

@@ -150,6 +150,9 @@
  y: float[10,20] --> coordinates along the first two dimensions
  z: float[30] --> coordinates along the last dimension
 
+ Note that each signal value ``data1[i,j,k]`` has axis coordinates ``[x[i,j], y[i,j], z[k]]``.
+ The same goes for the auxiliary signals ``data2`` and ``data3``.
+
  4. An example without :ref:`AXISNAME_indices </NXdata@AXISNAME_indices-attribute>` attributes::
 
  data:NXdata
@@ -162,7 +165,7 @@
  x: float[10] --> coordinates along the first dimension
  z: float[30] --> coordinates along the last dimension
 
- This implicitely defines `@x_indices = 0` and `@z_indices = 2`. Note that the second data dimension has no coordinates.
+ This implicitely defines ``@x_indices = 0`` and ``@z_indices = 2``. Note that the second data dimension has no coordinates.
 
  </doc>