Membean's primary focus is the development of a robust vocabulary. While we do have cloze questions where students are expected to spell target words multiple times, spelling is not an explicit focus. Spelling is only orthogonally related to word knowledge, especially at the middle and high school levels; spelling is more relevant for elementary school children.
During cloze questions, we expect a student to spell just the first 3 letters of a word. If a teacher wants students to spell answers fully, she can turn on the full spell option in student preferences (See: How do I modify student training preferences?).
Students also fully spell the word as an exercise the first time they see it. This has a dual benefit: it not only helps students learn to spell the word, but also slows down the pace with an activity, which helps to ensure that a word is explicitly registered in memory.