Looked in UV light?

Hello,

I bought a UV disinfection device to disinfect my cell phone, etc.
It was a really cheap one and the safety instructions actually said that the light would automatically turn off when you opened the lid.

Then, to test it, I opened the lid, but the light didn't go off and I was staring straight into the harmful UV light.

Is this harmful or harmless for those few seconds?
Of course, I will inform the manufacturer about the defective device.