My first grow! Start with good genetics!

You want 400 ppfd in this stage (up to 600 ppfd with CO2). Look up a "ppfd map" of your light. Put it at the recommended level and leave it. You can save a lot of electricity by dimming it but you need a lux meter at minimum or a PAR meter if costs don't bother you. Without measuring the lower power somehow, you won't know if you're getting the right amount of light to your babies.

If you can switch low the dimmer at 20% for first 10 days at 16 inches. After follow the 16 inches whit maximum of 30/40% of light power. Try to see the manufacturer directions. 👍

That should be a good distance. Keep an eye on them.