To be clear, you are using the IM100 meter, our first product. I’m afraid your meter is behaving as expected. That product has difficulty accurately measuring the color of cool LED lights.
All white LEDs are made by placing a phosphor material on top of a blue LED. The blue LED causes the phosphor to emit yellow light, producing white light. The blue LED’s light is a very narrow, pure shade of blue, with a typically 445 to 455 nm. That’s less than 2% of the range of colors visible to humans.
Despite our best efforts, the meter’s response in that region is slightly inaccurate. That causes white LED readings to be off by about 400K to 800K. The meter’s error is typically +/-50K for most natural and broad-spectrum light sources. Even warm LEDs, with color temperatures of 4000K or less, are accurately reported. It just happens that cool LEDs are a problem.
WE expect to release an updated version of the meter by the end of the year which, among other things, improves the blue accuracy and thus white LED color temp readings.