So I've seen a lot of questions about the oil crisis, but what I still didn't figure out is how the broker (providing you the ability to buy commodities) calculates their prices in respect to contracts.
I have an account on XTB. When the May contract was ending the oil took a dip and I bought some for 7 per barrel. This dip can be seen on their graph https://www.xtb.com/en/trading-services/range-of-markets/commodities-trading/oil-wti. But the May contract for oil went negative and June contract was around 10 bucks when I was buying it for 7, so where the price of 7 bucks came from?
I've read that they use something called rollover but if I understood correctly that only means that when the contract expires it automatically obtains you a new one and recalculates your holdings accordingly.