Most 20L tanks are only 12" deep. Is that what yours is?
If so, the Current Orbit led (that I dislike) should be fine for your tank. It should even be OK for sps coral. They make more than enough PAR for tanks of 12" to 16" deep and they have a good spectrum. You don't need more light until you go deeper. The issue with your fixture is that it doesn't have enough punch to get PAR deeper tan 16" or so. They use 0.5 watt leds when everybody else uses 3 watt leds and some are even going to 5 watt leds.
BTW, the reason I dislike your light is that the manufacturer markets it as if it's a really good fixture for coral at 24" deep. And that's pretty much a lie unless you want all mushrooms below 12" deep!