Anki treats small steps and steps that cross a day boundary differently. With small steps, the cards are shown as soon as the delay has passed, in preference to other waiting cards like reviews. This is done so that you can answer the card as closely to your requested delay as possible. In contrast, if the interval crosses a day boundary, it is automatically converted to days.
Day Boundaries
Learning Steps
Relearning Steps
Anki shows me all my red cards before the new ones. How do I make the new ones come first?