How to count the Brightness ? Strip Light

[KevinZ]

So recently I want to see what light do I use.
(Low - Moderate - High)
I never try to count this so idk how many watt/liters I have
I use strip light and it said 2 watt / Meter!
I use only 2.8 Meter on my 50 Gallon tank. When I tried to count it I only get 0.0008-
Did I miss count or that's the correct watt/Liters?
Should I change my Light? It's been almost 3 years and my plant living happily lol.
(Ex For my Carpet Plant that Alr dead bc of 3 day shipping)

 

[Byron]

Someone who knows this light unit may be able to help (I don't), but if the plants are thriving after three years, I would not want to change it, it must be sufficient.