Connecting to WebSocket API costs 1 weight. Then you immediately send a "time" request which costs 1 more weight. Thus you end up seeing 2 reported in request response.
Weight usage is reported in HTTP headers during connection, but unfortunately connection headers are not available in "open" events.
Hello, what’s in the documentation for method: "time" response, is only an example.
To understand more about Rate Limits, please consult at Binance API Documentation.