"To assign a number" means to give or allocate a specific numerical value or identification to something or someone for identification, tracking, or categorization purposes. Full definition
Applicants fill out various forms and are assigned a number of points (based on factors such as a person's skill set or language ability, for example). (aclrc.com)
Interested adopters arriving early can enter through our main entrance door after 8 am to inquire about being assigned a number for when visits and adoptions begin at 11 am. (animalwelfaresociety.org)
You can also personalize notifications by assigning numbers to specific people or apps. (tomsguide.com)