People are just now finding out what this strange mark on the shampoo and conditioner means. TikTok user reveals what this sign is for - and it turns out that it provides very important information to the consumer.
If "6M" appears on the small container, the product is effective for use for six months from the moment it is opened. Some even claim that you should write the date you first opened the shampoo on the bottle itself, because you may not remember later how much time has passed since the first use.