An instrument may apply a multi-day swap on its designated rollover day. That day is not the same for every instrument.
The adjustment accounts for weekends or non-settlement days. It may be a debit or credit depending on trade direction and the current swap value, and holidays may change the timing.
In the correct MT4 or MT5 account and server, open Market Watch, right-click the complete visible symbol, and select Specification. Review Swap Long, Swap Short, and any triple-swap day or factor field. Field names may vary; the current Specification and account controls are authoritative.