Currently Web Experimentation Audience Attributes only support values as string types. Adding support for number values (floats, integers) would allow for more complex and granular audience membership.

Customer provided example: An audience for visitors who have less than 100 subscriptions. The Audience Attribute numSubscriptions would be a number value of the total number of subscriptions the visitor has. This attribute could be used to build an audience for all visitors with less than X (ex. 100) subscriptions.