Four keyword tools, four exports, twelve thousand rows combined. The real number of distinct terms is probably closer to five thousand, and the difference matters because it changes what you promise.
Deduplicate before you scope anything
Stack the exports and remove exact duplicates. Every tool surfaces the same head terms, so the overlap is always substantial — typically a third to a half of the combined total.
Why the inflated number is dangerous
Scoping a content programme against twelve thousand terms produces a plan and a budget that both assume twelve thousand opportunities exist. When the real figure emerges mid-project, the plan does not shrink gracefully; it just becomes wrong.
Then go looser
After exact deduplication, run a case-insensitive pass, then sort words within lines and deduplicate again to catch reorderings. Each pass finds fewer, and the number that survives all three is the one worth planning against.
Try it: Remove Duplicates (Exact) on SeoWolf's Notepad.