The default for a deck is to randomize presentation of the cards. This can be turned off in the Details menu. For mini-books and sequential lessons you will want to turn this off. You can also enter a number of cards to hold "still" at the beginning of a deck. This is useful if you start with a mini-lesson.
By default the answer blocks for multi-choice and multi-picture are randomized by default. You can turn this off by using the item setting menu to the right of the editing screen in the deck editor.
If the deck is non-randomized, each play of the deck will take the student through the whole deck. Keep that in mind when deciding deck length.
If the deck is randomized, students will get a random selection of 20 cards each play unless you change the default number of cards per play in Details.
The random selection will pick cards the student has seen less frequently over cards they've seen more frequently so the student will run through the entire deck before seeing repeats. This means the first few run throughs of a deck with many cards will be harder than later run throughs. Again bear this in mind when deciding how many cards to include in a deck. If you want materials to get progressively harder, we recommend breaking items into smaller decks and then creating a bundle showing progression (levels 1-n).