Percentages are by volume — the standard method for DIY starters. Flavours are treated as PG-based; grams use approx. densities (VG 1.26, PG/flavour 1.04 g/ml); drops ≈ 20 per ml and vary by dropper. Strengths are shown in mg/ml. Handle concentrates with care, follow local guidelines, and keep out of reach of children and pets.