update release notes again

Author: KrisThielemans

documentation/release_6.3.htm

@@ -144,13 +144,21 @@ <h4>Changes to examples</h4>
   <h3>Bug fixes</h3>
   <ul>
     <li>
-      Fixed a bug in the SPECTUB matrix (introduced in 4.0) that effectively inverted the "x" (horizontal) axis for the
-      attenuation image. This resulted in an inconsistent attenuation image orientation compared to the reconstructed emission image. 
-      This axis inversion is now reverted, so if your scripts are using an attenuation map, you need to ***remove**
-      calls to `invert_axis x` (or code to that effect) to get correct results.<br>
-      See <a href="https://github.com/UCL/STIR/pull/1631"">PR #1631</a>".
-      </li>
-    </ul>
+      Fixed a bug in the SPECTUB matrix (introduced in 4.0) that effectively inverted the "x" (horizontal in-plane) axis for the
+      emission image as part of the projection. This resulted in the need for an inconsistent attenuation
+      image orientation compared to the reconstructed emission image.
+      This axis inversion is now reverted, so
+      <ul>
+        <li><strong>reconstructions of existing SPECT data will have an x-flip with
+          respect to previous versions of STIR</strong> (unless older than 4.0).
+        </li>
+        <li>if your scripts are using an attenuation map, you need to <strong>remove
+          calls to <code>invert_axis x</code> on the attenuation map</strong> (or code to that effect) to get correct results.
+        </li>
+      </ul>
+      <br>
+      See <a href="https://github.com/UCL/STIR/pull/1631">PR #1631</a>.
+    </li>
     <li>
       Fixed a bug in the scatter estimation code (introduced in release 5.1.0) if input data is 3D and "cylindrical"
       (there was no bug for "blocksoncylindrical" data).