The rule
A number is the strongest form of evidence, but it isn't the only form. When you don't have an exact one, reach for scale (how much, how many, how often) or scope (how much responsibility, over what) before you reach for an adjective. "Large," "significant," and "various" are what a bullet says when it has nothing more specific to say.
Why "significant improvement" doesn't work
The instinct, when you don't have a number, is to reach for an intensity word — "significantly," "greatly," "substantially" improved something. The problem is that these words are unfalsifiable and every résumé has a few of them, so a reader has learned to read straight past them. They don't make a bullet sound more impressive; they make it sound like every other bullet.
A specific, honest scale — even an approximate one — does more work than an unverifiable intensity word, because it's concrete enough that the reader actually pictures it.
Four things to count when you don't have a percentage
Scale
How many people, records, users, tickets, or dollars were actually involved? "Supported 40+ retail associates" beats "supported the team."
Frequency
How often did you do it? "Ran the weekly ops review for 8 months" is more concrete than "regularly ran ops reviews."
Scope of ownership
What did you own end-to-end versus contribute to? "Owned the onboarding flow from design through launch" says more than "worked on onboarding."
A before/after state
Even without a percentage, "cut the release process from a two-day manual checklist to a same-day script" shows the change without a single number in it.
What not to do: don't invent the number
If you genuinely don't know whether a change was 20% or 40%, don't write 30% because it sounds plausible. Beyond the honesty problem, an interviewer who asks "how'd you get to that number" and gets a shrug has learned something worse about you than the vague bullet ever would have. Scale and scope don't have that failure mode — "supported 40 associates" is either true or it isn't, and you know which.
Find the bullets that need a number
The Analyzer's Experience & Results category flags vague duties versus quantified impact, line by line.