Some instructors prefer that students either get credit or no credit for each Perusall assignment (i.e., pass/fail scoring). To do enable "threshold scoring," navigate to Settings > Scoring > Automatic scoring, create a new (or edit an existing) Scoring template, and insert a value in the Threshold score for credit field.
If a threshold is present, then all scores in the Gradebook will either appear as 1 (meets threshold) or 0 (does not meet threshold). For example, if you keep the default assignment score scale of 0-3 and set a threshold of 2, then students' scores will show as a 1 if their score would have been a 2 or 3, and will show as a 0 if their score would have been a 0 or 1.