In the video it said to turn off the room lights and he did not run the test until the pointer topped out and/or declined any amount, I wonder if it could be within 10% or even 5% accuracy?
There's not much detail on it and the build looks hand made, also it said " some place may not be perfect " are they talking about the fit and finish because I can see the digital read out is a tiny bit out of square and the usb port looks a bit over cut out at the bottom where they fitted it as well as the sensor hole looks hand cut with the penciled on round hole marks still partially showing, but if it's reasonably accurate and repeatable to even 10w I would be tempted, but it says nothing about the usb port or what else it may or may not do......it could be a diamond in the rough, but that's just me being hopefully optimistic.