I have a (D)ropper with a (T)arget block next to it. I have a (R)edstone (C)omparator next to the Target block, facing away from it.

So the layout is: DTC->

-> is to show the direction the RC is facing.

When items are in the Dropper, the Comparator does not detect the Dropper's state. In the provided screenshot, there's one Bone Meal in the Dropper.