Rollover is the fee which is based on the swap rate for the underlying currency pair, and is accrued or charged at midnight if you have an open position which has to be transferred to the next day.
It is you who decides how long to keep your position open. Please note that the swap points can be positive or negative in value. In the first instance, the rollover is accrued (added) to your account, while in the second case it is deducted (withheld).
The amount you will pay or receive for an open position depends on the currency pair you trade, since the transaction with any currency pair is a purchase of one currency and a sale of the other.
Rollover = (Swap rate/10,000) × Position × Number of days
When JPY is participating in the currency pair:
Rollover = (Swap rate/100) × Position × Number of days
In this way, the sum is in the second currency of the currency pair. If the currency of your account is different, it needs to be recalculated in the currency of the account through conversion of the corresponding close price for this currency.