❔ Ef Core Unique Index Problem

Hello guys, I'm looking for a solution for a problem. As seen in the pictures, I have FirmId, LCode fields for which I created Unique Index. My problem is that when I insert a data that is in the database, even though I send different data after getting an error, "Cannot insert duplicate key row in object 'dbo.Warehouses' with unique index 'IX_UNIQUE'. The duplicate key value is (1, TEST5)." i am getting the error. But the data I sent later (1, XXXXXXXX). Why is there such a problem?