A 1% difference is negligible, I don’t think I’d even notice. It doesn’t matter if it’s exactly that precise, as long as it doesn’t leak from the RTA. 
But I don’t know if I should stick to 30%. The bottle and the manufacturer’s website say this much. Other sites say 20-25%. So far, it’s only leaked once. I hope it doesn’t happen now I need to save because I only have 4 dl of VG left