This diagram is widely copied in books and in websites. It's been taken from Odum(1956).
There's a problem I find at the bottom of the diagram. The energy content of carnivores (Trophic level 3) is shown 0.3 units which I think is supposed to be 0.015 units according to 10% law.
It is quite unusual that a diagram that is largely redrawn will have a mistake in it. I'm a unaware of something that the diagram shows?