add small explanation

Author: saranti

galleries/users_explain/axes/legend_guide.py

@@ -264,7 +264,9 @@
 
 # %%
 # As you can see, "Line 1" now has 4 marker points, where "Line 2" has 2 (the
-# default). Try the above code, only change the map's key from ``line1`` to
+# default). We have also increased the length of the handles with the
+# ``handlelength`` keyword to fit the larger legend entry.
+# Try the above code, only change the map's key from ``line1`` to
 # ``type(line1)``. Notice how now both `.Line2D` instances get 4 markers.
 #
 # Along with handlers for complex plot types such as errorbars, stem plots