If it's not difficult for you, please...

Good day, Sergey! There is no main source of information in the world, from which all platforms would broadcast quote values. Your opportunity to profit is not in a specific quote value, but in the ability to predict where the price of a certain asset will move based on historical data. If a trader works on our platform, he analyzes the data that we broadcast.
As for quotes, our company uses quotes of the largest investment banks and broadcasts to the platform a weighted average of the best available in the “stack” of buy and sell prices. This allows the chart to react quickly to changes in market conditions, but not to go beyond the best buy/sell price, which protects against non-market manipulations by traders.
Forex – aka currency international interbank – does not have a common clearing center (“bringing together” the transactions of different counterparties). Therefore, major international banks, being so-called liquidity providers, give information about interbank transactions to different companies. These are so-called indicative quotations. It is the indicative quotes that are presented on all charts. They are then used by anyone who needs them, such as trading platforms.
You should also take into account that in options the quotes are built as (bid + ask price)/2, while in brokers’ terminals the price is always built at the bid price by default.
Olymp Trade is a reliable trading platform with three years of experience and a member of the International Financial Commission. We value our reputation and do not give in to provocations. We are confident in our terms and conditions.

Sincerely, Olymp Trade Quality Assurance Service.