Blocking the wrong level either over-blocks (cancels other bookings) or under-blocks (lets a booking happen you can't honour). Pick deliberately.
Block at room level
One room is unavailable (maintenance, personal use of that bedroom).
Other rooms can still be booked.
Block at accommodation level
The whole venue is unavailable (full closure, fumigation, owner stay).
Every room blocks at once.
How to pick the level
On the calendar, before blocking, pick the scope from the dropdown next to the date range — "Room", "Accommodation", or "Listing".