To exclude text from the similarity report according to its size, click the red filter icon from the similarity toolbar. If the similarity layer was inactive, it will now be activated, highlighting all on-paper matches.
From the Filters and Settings side panel, use the radio and text boxes to determine which exclusions should apply to the paper's similarity report. You can exclude sources that are less than a certain number of words, or a certain percentage of words. For example, filtering by 10 words will exclude all sources that have a cumulative number of matching words that are less than 10 words in length.
Click Apply Changes to confirm this change. This will repaint the similarity report with your change now reflected in the assignment.