Considerations for converting a LED Bulb from AC to DC power
Your calculation is incorrect. When you connect LEDs in series, the voltage required increases, but the current through the string is the same as for 1 LED. (The same electrons are flowing through all LEDs).
So if 1 led requires 8mA at ~8V, then 5 LEDs will require 8mA at ~40V.
Two of these strings in parallel would require 16mA at 40V (if your math for 1 led is correct).
An easy check you could have done is to calculate the wattage. 450mA at 40V would be 18W, where it should be around 5.
Your initial assumption of 8V and 8mA for 1 led would give a wattage per led of 64mW. So for all 10 leds we're looking at 0.64W, which is not correct. Again it should be around 5W.
You should hook up the driver again, and adjust it until 1 led is drawing 0.5W. Then redo the subsequent calculations with the current and voltage you measure.