Laws of UX
Miller's Law
Working memory holds ~7 (±2) items. Chunk information into groups of 3–5. Phone numbers, card numbers, and step indicators all use chunking. Especially critical for users with cognitive disabilities.
In plain terms
People can only juggle a handful of things in mind at once — so break long numbers and lists into small chunks.
Why this matters
Overstuff a screen or a number string and it overflows working memory — people lose their place and make mistakes. Chunking protects users with cognitive and memory disabilities in particular.