anything over %40 will do the trick.%60 is great,yours looks to be %70 this is great too but need some fresh air circulation.The thing is,seedlings with no roots can absorb nutrients through leaves with the help of humidity.But this is critical , humidity is very much related to air temperature.So, if your humidity is below %40 and temps are above 30C,this is something to prevent because your buds will be fluffy,plant won't get enough nutrients,you don't want it to be.I live in a very dry area,humidity is now showing %15 with ventilation on, glad I'm about to chop my last plant that's why I don't care about it.But if I were to start a new grow with %15, I would definitely buy a humidifier just to bring it back to %50. High temps with low humidity is BAD , lower temps(20C-25C) with low humidity(30-40) is OK, lower temps with optimal humidity(40-60) is great.Again,if your plant grows well,looks healthy and drinking with no problem and you have a low humidity,NO PROBLEM at all.just try to keep the conditions stable