Some weapons like storm bolters and multi lasers fire multiple shots. Where this is the case the number of shots a weapon can fire is noted after its type. For example a multi laser can fire three shots in each shooting phase so its type is noted as Heavy 3.
Multiple Shots
Source: Core Rulebook 3E, p. 56
Weapons that fire more than one shot per shooting phase note the shot count after their type, e.g. Heavy 3.