How matching works
Quick answer
Matching compares each staged filename with every published post of the chosen type — its title, and any filename already in the target field — and proposes the best fit with a confidence score.
It proposes. It never decides. Nothing is written to your site as a result of matching, and every proposal is yours to accept, change or ignore on the Review & Resolve step.
What you choose first
Two things, on the Match step, and they are per batch rather than global:
The post type. Whatever holds the documents — pages, a custom type, anything registered and public. The plugin looks at your site and suggests the types that actually have a field holding file paths, so this is usually a pick rather than a guess.
The meta field. The custom field that stores the file. You can name more than one, separated by commas; they are tried in order, and the first one with a value wins. That matters for sites where the same kind of document lives in different fields on different posts.
What is compared
For each file, the plugin scores its filename against two things per candidate post: the post title, and the filename already sitting in the target field if there is one. The better of the two scores is the one that counts, so a file named after the existing document matches even when the post title is worded differently.
Before comparing, both sides are normalised: case and punctuation go, a built-in list of generic words is ignored, and any variant groups you have configured treat their members as the same term.
The two thresholds
Accept (0.65 by default). At or above it, the row is proposed as Matched. Below it, the row is Needs Review — the plugin found something but is not confident enough to put it forward.
High confidence (0.85 by default) changes nothing about the outcome. It only decides where the score indicator turns green, so you can scan a long list and see which rows deserve a second look.
A file with no candidate at all also lands in Needs Review, with no proposed post.
Re-running it
Safe, and expected. Changing the field or the variant groups and running matching again only touches rows still at Staged, Matched or Needs Review. Anything you have already decided — Skip, New Page Needed, Confirmed, and everything already replaced or verified — is left exactly as it is.
So the order that works is: run matching, fix what is wrong by hand, change a setting, run it again. Your corrections survive.
What the free plugin does not do
It does not learn. A correction you make by hand is applied to that row and not remembered for the next batch, and there is no managed list of abbreviations or ignore terms. Variant groups are the one piece of vocabulary you can edit, and they are yours to write rather than something the plugin accumulates.