Only one. The sensor itself is about as big as 2 coins of 2 Swiss francs (one upon the other). Almost all space in the box is used for the special mechanism, in two parts, that implants under your skin a very thin filament attached to the center of the sensor. Durting the implantation, the sensor is glued to your skin and then transmits its readings either to a special device or any nfc capable smartphone/app. It should work during 7 to 14 days. So one box = one sensor gives you continuous glucose monitoring for about two weeks.

Unfortunately the manufacturer does not indicate this.