A seat is one accepted member of your workspace — someone you’ve invited who’s actually joined, not someone you’ve merely sent an invite to.
What this means for you
Seats in use is a live count of active members. An invite that hasn’t been accepted yet doesn’t count, and doesn’t bill, until the person actually joins.
The Seats panel on Plan & seats shows this same number as your active member count, right next to Manage members and Add a person links.
The count updates the moment someone joins or is removed, and your billed quantity is kept in step with it automatically — you don’t have to tell WorkMonitor how many seats you’re using.
A workspace with no active members yet still bills at least one seat — a plan is never billed for zero.
Related
Plan and seats (overview)
Can I change plan in the middle of a billing period?
What happens to our data if we cancel?