Let’s learn about the M on the circle

Let’s learn about the M on the circle
Most people, when they buy any product, pay attention only to the expiration date (Expiry), but a large part of them do not pay attention to the shelf life of the product (after opening).
I mean … if a product has a validity period until 2023, for example, it is not that it can be used until 2023.
There is a sign shown in the picture below (like the shape of the open box) written on it with a number and after it the letter M, which is the abbreviation of month
It is written especially with creams, ointments, lotions, toothpastes, etc.
1 m➡️ The product is valid for one month after opening
3 m➡️ The product is valid for 3 months after opening
6 m➡ Product valid for 6 months after opening