people.increment()

people.increment() is a method, in the style of some tools, that raises or lowers a numeric property on the user's profile by a delta instead of overwriting the value.

This call is from the profile-operations family — things done on the user rather than on an event; incrementing suits counters such as total purchases or a points total that must accumulate over time. Its advantage over setting is that the client need not know the prior value and just says add one, which helps when events are spread across devices. But the same incrementable-property risk applies here: a network retry can raise the counter twice. The more fundamental point is that this pattern assumes a writable user-property store; tools whose unit of analysis is the event often compute these aggregates from the event stream at report time instead of holding them on a profile, which is both safer and auditable.