Auto-Allot reassigns ALL students in the selected section alphabetically and overrides any existing roll numbers — this is not additive, so double-check you have the right class/section selected before confirming. Every roll number, whether auto-allotted or typed manually, must match the Roll Number Validation Pattern (Regex) set under School Settings — if Auto-Allot shows a 'does not match pattern' error, that's the setting to check first.