Understanding “duplicates"

I purchased this app for two reasons; to locate and remove unnecessary duplicate files in my computer and to counter a what appears to be an unfounded negative review. A poster gives it one star because it did not locate any of “hundreds of duplicates” in art files that he keeps many copies of made at various stages of completing paintings. A file with the same name having additional work done to any number of sequential copies is not a duplicate. Each is a unique picture of the painting at progressive stages, something I suppose the app detects by either size or comparison of contents.

sensordev about Duplicate Finder - File Clean