With Stream, you can access earnings right up until payday. So, for anyone on an Arrears schedule like yours, there will always be a date range where you can access wages from two pay periods at once: the previous pay period (as you have not been paid for this yet) and the current pay period (the one we are in right now). We call this the Arrears Zone.
Any transfers made during this Arrears Zone may access earnings from either your previous pay period, the current pay period (so will be carried over to your next paycheck), or both (split across paychecks then carried over). Which pay period(s) your transfers come from will depend on how much you have earned at the time of transferring:
More details of how this breakdown happens can be found on the balance calculation page by tapping the ℹ️ icon in the Track header.
You can check when an individual transfer will be settled by selecting Transfers on the Track page of the app, tapping on the transfer you would like to view, and then scrolling to Settlement details.