The job: know what each retainer is actually consuming
A retainer is a promise to deliver a certain amount of work for a fixed fee. The tracker answers whether that promise is being kept, exceeded or under-delivered, and it needs to answer in the middle of the cycle rather than after it, because that is the only point at which anyone can act.
How it is done today
The most common method is a shared sense of which clients are demanding. Everyone in the studio knows, nobody has a number, and the account is repriced only when someone finally loses patience. It is remarkably accurate about which client and remarkably vague about how much.
The next version is timesheets filled in on Friday for the whole week. Those produce a number, but the scope tag is guesswork by then, and the report arrives after the month has already been over-serviced. Late data describes a problem; timely data prevents one.