I'm sure there were instructions but they're long gone.
It's been wedged in that spot inside my WE4 for 16 years at least now.
I only think about it when I see lots of red lights.
Caspers audible gauge is what I use for racing in both cars along with direct scan and the scanmaster.
When I was running the Kenne Bell chip it lit up a lot more with transitional knock and shift knock at 17-18psi. boost that chip ran on pump gas.
I don't look at it much anymore with the alky flowing well.
Only heard my car knock badly once at the track and it was full red and the Caspers audible was screaming too.
Still using the original headgaskets but not really using that detector for tuning anything seriously anymore.
I would say it's a bit more sensitive than other scan tools but if you have a scanmaster you may want to try to correlate the lights to that device, although I didn't have much luck doing that with Caspers LED gauge and the scanmaster on my GN most likely to timing issues with a real time gauge and the ALDL data stream.
I would check out what's causing it to go off when starting and shifting into gear first.