Unfortunatly, many lighting mfg's inflate light output on their items, so the best way to determine light height and intensity is by actual measurement.
I use a free app called Photone.
For seedlings, you want 10-12 DLI if light. make sure to set the app to the correct number of hours.
If the light gives an even pattern, 12-6" away is not unreasonable.
Too much light kills plants fast. Very hard to kill with too little light.
View attachment 1627893