The seating during the 24 ours of OLCI is dynamic, it may well show as blocked in EF at some points, then later available for selection.
The only time you can check it is still blocked is after OLCI closes.
Depending on the reason for the block, the seat may well show as occupied on the BA App is it has no way to distinguish between blocked seats and occupied seats.
No idea what "number seven in the sequence" means, what your sequence number during OLCI is has no bearing on if the seat next to you will remain clocked or not.