This counter indicates whether the cell is available for traffic or not. It is as simple as that. You may have other counters which provide availability per TRX (trx avaiability).
If trx3 is down, the rest of the cell remains available.
If cell is not available, then trx0 is not transmitting bcch, then your counter is stepped.
Now, based on the values you are seeing, it looks like the value “3600” indicates that the cell is indeed available.
You should check the values for a cell which is apparently “down” or “locked”, and see if they increase or decrease.
I suspect they decrease..? You gotta try… If all your cells are “Up”, consider locking a cell artificially for 30mn 😉