How does Binance calculate the open and close values in the candle plot for Spot Trading?

Hello. I've heard that the open and close values are associated to the first and last transaction of the time vary (day, week...). Nevertheless, I observed the open value is identical because the close value of the earlier bin, which sounds weird to me. As cryptos are decentralized, shouldn't we have now totally different values for that? Couldn't we've got an outlier transaction within the first transaction of the day that is totally different from the last transaction of the day before today?

Additionally, prices in the dashboard (Spot trading) are calculated based mostly on only Binance transactions or other external sources (like other platforms)?