I would never, ever have a number in mind honestly. Especially something super low. Calipers are wildly innaccurate at low body-fat levels, and hydrostatic weighing CAN be reasonably accurate if you are really, really careful and follow very specific breathing and movement protocols, but even then DEXA is still the only thing accurate and precise enough to be relied upon for a number that means anything objectively. Calipers are great for relative progress, but the numbers don't mean anything in objective terms because there is huge error built in.
In my opinion the ONLY thing that matters is how you feel. There's no decreased health risk for dropping lower than 12-15%, and there are (possibly) health and (definitely) daily life effects of dropping below certain thresholds that are not great either. We throw around numbers like 6%, but that doesn't mean anything if it comes from calipers. What we do know is that all of us have a point beyond which we feel like crap no matter how perfectly we do things. Why try to go beyond that?
That's just my opinion, but there it is. Be where you are happy about how you look and feel.