You don't need to use a Clock in the App because the sending of data is already timed in the Sketch and the BLE blocks deliver the data accordingly. So omit the Clock but observe how the graph should be updated with the values.
It is because a List of values is expected and thus, if possible, should be processed as such. However, the Arduino is not delivering a List (two or more values sent one after the other), it is sending a concatenated String of two values to suit the graph extension, and therefore in this case 'select list item' might not work. However, you can try it, it works here if I make a test List of one, but my test is not using the value as received via BLE.
If 'select list item', does not work, we have to clean-up the String by removing the brackets, but it should work as per ABG's example.