Credits are how usage is measured. Every interaction with the AI draws from your company's shared monthly pool, and the cost depends on the depth of the request.
As a guide:
Asking a quick question: from 1 credit
Refining or editing a document section: 2 to 4 credits
Analysing uploaded project documents: 5 to 10 credits
Generating a full document: 10 to 15 credits
Exact costs depend on the depth of each request. Simple asks cost little; deeper work draws more.