If a scan misreads an answer - or a student's mark was genuinely ambiguous - you can correct it directly on their results page.
Most scans need no correction at all. You might want to edit a result when a question was flagged blue (an ambiguous mark) or yellow (possible glare) in the Question Breakdown, or if you spot a genuine misread while reviewing a sheet.
Open the student's result page and tap Edit. This puts the Question Breakdown into edit mode, where you can tap any question and select the correct bubble.
Once you've made your changes, tap Done to save. The student's score and the Question Breakdown recalculate automatically to reflect your edits.
Correcting a student's ID number is a separate action from editing answers - see How to Use the Student ID Section for that.