Again... Wall draw and actual output are 2 different things.So I can use watts to see how much light I getting, if I understand you?
And if I want amperage I must buy multimeter.
But if by calculations I get 260W (above quote), then obviously amperage is higher than 1.05A on DC side. Up to 1.25 or 1.28A as you said.
Take a multi-meter and test your actual COB chip. This will tell you what you are ACTUALLY outputting.