Payment discrepancy

[Vince65]

Can anyone help me out here. I have my first guests arrived yesterday. I have been informed several times to expect £192.80.after airbandb have taken their cut .  I have just had my paypal account credited with only £187.30. This is £5.50 short. Pay pay do not charge at all. Apparently it is because of the exchange rate dollars to pounds has changed. This being the case is it always going to be an estimate that is quoted by airbandb based on the exchange rate when the quote is made. I dont understand why payment from my guests is made in pounds then it is converted to dollars and then paid to me in dollars making it subject to fluctuation. Am i missing something.