Subject: IBKR question
I just bought BRK puts. As I didnīt have enough USD cash I converted some GBP into USD to cover the missing USD amount for the trades I intended.

Then I made the BRK puts trades. To my surprise not the USD account was debited was instead my GBP account, with actually more GBP converted by IBKR after my own conversion order. Is this because the conversion was not settled yet? That IBKR just grabs whatever cash account you have and eventually convert enough of that into USD to cover the trade(s)?