Question: why does kosher salt have less sodium?
Answer: Kosher salt and some sea salts may have larger crystal sizes than table salt, so they may have less sodium by volume (e.g., by teaspoon or tablespoon). A teaspoon of table salt has about 2,300 mg of sodium, but a teaspoon of sea salt or kosher salt may have less sodium simply because fewer crystals fit on the spoon.