Fix error in mask transparency notes.

Author: jeffcarlin

03_Image_Display_and_Manipulation.ipynb

@@ -385,7 +385,7 @@
     "afw_display = afwDisplay.Display(frame=fig)\n",
     "# set the image stretch algorithm and range\n",
     "afw_display.scale('asinh', 'zscale')\n",
-    "# set the transparency of the mask plane (1 = opaque)\n",
+    "# set the transparency of the mask plane (0%=opaque, 100%=transparent)\n",
     "afw_display.setMaskTransparency(80)\n",
     "# set the color for a single plane in the mask\n",
     "afw_display.setMaskPlaneColor('DETECTED', 'blue')\n",