The burn must be done from the profit that already received by the company. This is what we have called that as a healthy burn. Some people may think that burn must be done from the pre-mined coin as well.
that's true but the main purpose of burn to decrease the coin on circulating supply and this will make the total supply will decrease.
I also add a little that by burning, making the tokens that have been owned by several investors and participating people experience an increase in price but many factors will support an increase in the price of a coin they hold. But burning will greatly make a difference to that token or the project.