There's a feature where you can also gift bloxbux, but you cant pick how much Robux you want to spend to buy bloxbux, its a set amount or none.

For example, if I wanted to spend one hund Robux on bloxbux, i could only spend 95 (250 bloxbux plus 50 bloxbux option) and not the full hund.

Add a feature where you can set the amount of Robux you want to spend and you would get a set amount of Bloxbux for one hund Robux.