Only one withdrawal per month is possible, debited from your account and sent on the last day of the month. This is because your funds are automatically placed in arbitrage pools from the first to the last day of the month, and it is too complicated, from an operational point of view, to make withdrawals during the month.
So it doesn't matter what day of the month you make your withdrawal request.
And this request does not affect your balance or interest of the current month. Your interest is calculated on the last day of the month and added to your balance. Your withdrawal is then deducted from your final balance.
Subject to a sufficient balance, the Withdrawal is executed on the last day of the month.
The amount sent in cryptocurrency is calculated at the time the funds are sent; the conversion is done on the arithmetic average of the BTC-EUR or BTC-USD exchange rates listed on 3 of the main platforms of the world market.