Up until 6288.5 generations ago, the count of B deme was 5107. Following that period, it increased to 7528, where it has persisted until now.
time_units: generations
demes:
  - name: B
    start_time: .inf
    epochs:
      - start_size: 5107
        end_time: 6288.5
      - start_size: 7528
        end_time: 0