increment
Increments the value of an custom attribute by a given amount. If no amount is given, the by default it will be incremented by 1. Only integer and long custom attributes can be incremented. Attempting to increment a custom attribute that is not an integer or a long will be ignored. If you increment a custom attribute that has not previously been set, a custom attribute will be created and assigned the value of incrementValue. To decrement the value of a custom attribute, use a negative incrementValue.
Return
whether or not the custom user attribute increment was successfully logged
Parameters
key
The identifier of the custom attribute
increment
The amount by which to increment the custom attribute