This occurs on both the desktop version 2.1.44 and the iPad latest beta and the android version. On the one hand, this implies it is my interpretation, on the other, they probably have the same scheduler.
I often review ahead on a deck, when I notice a spike in the not too distant future and I want to head off a “big day” for that deck.
Some cards seem OK in their next review date (particularly those in the more distant future, but others seem strange. I can’t identify a pattern.
For example today I made a custom deck of reviewing ahead for exactly 3 days (prop:due=3) for a deck, and then on answering one of the cards it had the next reviews (buttons on the bottom) of <10m, 1d, 2d, 2d.
I can’t see how a card due in 3 days, at its easiest, would now be due in 2 days. Even a rounding “error” should not produce that result, in my opinion.
I have also modified the setting for Interval Modifier to be 75% (not sure if this is relevant, nor am I sure coincident with this occurring).
Is this just my interpretation of how reviewing ahead should work?