Thanks Katja!
Yeah, the "interval" is the time between reviews on a certain card. So if you get a card correct, and the interval becomes 5 days, then you'll see the card again in 5 days.
The first interval will be about 1 day. As you continue to get the card correct, the interval will increase.
Here is basically what you are missing:
Last review + interval = due date
Imagine you have 200 cards. Imagine all your cards have an interval of 5 days. (the "≤ 1 week bucket" ; You've gotten all your cards correct a few times)
This 5 days does not say with a card is due. It only says interval.
You've been studying your 200 cards over many days, and you review maybe 30 each day. So cards are staggered.
They all have same interval, but their due dates are all different because you reviewed them on different days (in our example).
This is a long winded explanation that hopefully helps.
Even more info:
https://orangeorapple.com/Flashcards/AboutSR.aspx