If you are using the trending tool in Control Expert and you have selected variables to be scanned by this tool, you can choose to use the "Fast scanning" function. This is optional, but is recommended. That is why there is a warning when you build. To avoid this warning, you can either select "Enable Fast scanning for trending" from the Project settings or you can untick the scanning property from all variables (if you are not using the trending function). Note, the scanning property is not enabled by default.