Those are just preflowers, no worries.
I use 16/8 due to limitations of my dimmer knob all the time. Even the lights i have greater control i just keep vege on 16/8 just for consistency. Even 15/9 is probably safe, but to avoid that 1 out of 100 oddball, stick to 16 or more hours. (technically it is a longer uninterrupted dark cycle that causes flower phase, but it has to add up to a 24h cycle either way.)