@kpakpa There is something called a rollover with futures contracts. Since they have an expiration date, once it’s reached, your position is rolled over to the next futures contract. You had a position with Oil-20Mar which is now rolled over to Oil-21Apr.
Since there’s a difference between the prices of both these contracts - an adjustment must be made to cover the difference. The adjustment is equal to the difference in price between the two contracts times the quantity you own. You can find the exact adjustment amount in the app.
Rollover of futures contracts is industry standard, it’s not something specific to Trading 212.
You can learn more about it here:
https://www.trading212.com/en/Frequently-asked-questions?cId=12
And from the creators themselves: https://www.cmegroup.com/education/courses/introduction-to-futures/understanding-futures-expiration-contract-roll.html