Where each limit comes from

The source of each limit in the rules for a page. The rule numbers are those of What a page contains, section 5. The guides behind the other rules are on References on writing documentation.

Rule is the rule’s number, Limit what it allows, and Source the guide that gives the figure.

Rule	Limit	Source
5.1	a title of 65 characters	GOV.UK: write clear titles
5.2	a sentence of 25 words	GOV.UK: use clear language
5.3	a paragraph of 3 to 5 sentences	Google technical writing: paragraphs (three to five); GOV.UK: use clear language (five at most)
5.4	a list of 2 to 7 items	Microsoft style guide: lists
5.5	2 callouts	Microsoft Learn: Markdown reference
5.6	no step or prerequisite in a callout	Google developer documentation style guide: notices
5.7	15 links	GitLab documentation style guide
5.8	5 heading levels	GitLab documentation style guide
5.9	7 entries under a sidebar heading	Mintlify: navigation, which says top-level sections; the rule applies it to every sidebar heading
5.10	alt text of 150 characters	Microsoft style guide: alternative text