Clearer warning

Compiling-Grbl.md

@@ -28,7 +28,9 @@ _**NOTE: Before starting, delete prior Grbl library installations from the Ardui
 
 _**NOTE:**_ If your environment is clean and Arduino IDE compiler still throws "warning: [...] redefined" messages, you may need to _**uncheck**_ File -> Preferences -> "Aggressively cache compiled core".
 
-**_Compiling GRBL or Advanced Users:_** Most users are just fine with Grbl's default build, but you can customize Grbl by editing the `config.h` file in the Arduino library (**not where you downloaded it, it has been copied into Arduino Library**) folder. This file enables or disables all of Grbl's additional compile-time options. There are descriptions in the file that explains what they all do. Once edited and saved, just follow the steps above to flash your custom Grbl build!
+**_Compiling GRBL or Advanced Users:_** Most users are just fine with Grbl's default build, but you can customize Grbl by editing the `config.h` file. It is **extremely important** to edit the files **inside** the Arduino `library` folder **not** the folder you imported the grbl from. `config.h` enables or disables all of Grbl's additional compile-time options. There are descriptions in the file that explains what they all do. Once edited and saved, just follow the steps above to flash your custom Grbl build!
+
+**_Advanced Users:_** Most users are just fine with Grbl's default build, but you can customize Grbl by editing the `config.h` file. It is **extremely important** to edit the files **inside** the Arduino library folder **not** the folder you imported the library from. This file enables or disables all of Grbl's additional compile-time options. There are descriptions in the file that explains what they all do. Once edited and saved, just follow the steps above to flash your custom Grbl build!
 
 No fuss! No muss!