Add a note with the link to the spec override.

index.bs

@@ -3959,6 +3959,8 @@ The [=remote end steps=] with |command parameters| are:
 
          1. [=map/Set=] [=device pixel ratio overrides=][|navigable|] to |device pixel ratio|.
 
+            Note: This will take an effect because of the patch of [[#patchs-determine-the-device-pixel-ratio]].
+
          1. Run [=evaluate media queries and report changes=] for [=document=] currently loaded
             in a specified |context|.
 
@@ -10703,6 +10705,8 @@ Other specifications can define <dfn>console steps</dfn>.
 
 ## CSS ## {#patchs-css}
 
+### Determine the device pixel ratio ### {#patchs-determine-the-device-pixel-ratio}
+
 Insert the following steps at the start of the [=determine the device pixel ratio=] algorithm:
 
 1. If [=device pixel ratio overrides=] [=map/contains=] <var ignore>window</var>'s [=window/navigable=], return [=device pixel ratio overrides=][<var ignore>window</var>'s [=window/navigable=]].