Hi @Mcat!
Who would have known how friggin’ unreliable EVERYTHING is, even syringes?!
I couldn’t figure out which line to trust either, so here’s what I did (and still do): I use the syringe to have a basic idea of the amount and get the liquid out, then put it into a little bowl on my milligram scale and weigh it.
Water-based liquid weighs about 1 gram per ml, so 0.24 ml (your 0.12 mg at 0.5 mg/ml) is about 0.240 g.
If your liquid is not plain water, it can be a bit heavier than 1 g per ml, so you need to weigh 1 ml of your liquid once first and then use your own number.
Another option would be to dilute further. At a weaker concentration, your dose becomes a bigger volume, and the same tiny measuring error matters less.
Hope this helps!