Of the 5 transaction types in CampSite, only charges and discounts (i.e. what parents have been "asked" to pay) are designated towards specific sessions. Payments, credits, and refunds (i.e. cash you've already received) are not designated towards specific sessions.
With that, camps can generate their expected income per session by reporting on charges/discounts per session.
For camps that allow families to pay their balance on a payment schedule, this income will be received once all families have paid in full. If your camp requires all families to pay in full when they enroll (meaning, there are no families with an outstanding balance to pay later), than your charges/discounts would also represent the money you've actually received so far, since you're not waiting for those charges to still be paid.
To report on charges/discounts per session, use CampSite's financial Accrual reports. Click here to learn more.