message: Fix buffered_scatterer::capacity
diff: @@ -83,7 +83,7 @@ public:
  size_t capacity() const noexcept override {
  // TODO: get rid of magic number
  static constexpr size_t max_buf_size = 100;
  - return buf_.size() < max_buf_size ? buf_.size() - max_buf_size : 0u;
  + return buf_.size() < max_buf_size ? max_buf_size - buf_.size() : 0u;
  }
  size_t buffered() const noexcept override {
  