Add note about flow differences to retraction troubleshooting

calibration.html

@@ -777,6 +777,7 @@ <h5>I can't translate my test results to my own slicer! Other factors beyond the
                 <li>Maximum extruder feedrate: Your firmware may have a hard limit imposed on extruder movement that is below the retraction speed values you are attempting to use with the form above. You may need to use <a href="https://marlinfw.org/docs/gcode/M203.html" target="_blank">M203</a> to raise the extruder feedrate limit to try higher values for retraction speed. This potentially needs to be saved with <b>M500</b> if you want it to be permanent.</li>
                 <li>Travel feedrate: A travel move is one where the printer moves to a new location without extruding. The slower this move is, the more time filament will have to ooze from the nozzle and add to stringing. The default feedrate is set to 100mm/sec in the gcode generator above, and increases or decreases based on the user feedrate input. Matching this in your slicer is advised if these tests look better than your own slicer results.</li>
                 <li>Travel acceleration: This test does not manipulate travel acceleration but increasing its value may help reduce stringing. You can change travel acceleration with <a href="https://marlinfw.org/docs/gcode/M204.html" target="_blank">M204</a> and the <b>T</b> argument.</li>
+                <li>Flow differences: The gcode on this site originally had a flow rate of 90% when sliced. In Simplify3D and PrusaSlicer, this is called <b>Extrusion Multiplier</b>. Cura calls it <b>Flow</b>.</li>
                 <li>Linear advance: Linear advance, covered later in this guide, can drastically improve the accuracy of our extrusion. It has a significant impact of retraction (reducing the need), so after configuring linear advance you may need to revisit retraction.</li>
                 <li>Slicer differences: The gcode generated below was originally sliced by Simplify3D. The settings you establish should translate to your slicer quite well but there may be idiosyncrasies. For instance, Cura measures extra restart distance in volume rather than length.</li>
             </ul>