I believe it's because the properties for the bid/ask quantity and price have the same field name. See: https://github.com/binance/binance-connector-python/blob/e70769819d42b39a7c23f3475bf934454684cf26/clients/derivatives_trading_coin_futures/src/binance_sdk_derivatives_trading_coin_futures/websocket_streams/models/individual_symbol_book_ticker_streams_response.py#L34C10-L37C9