To access these symbols, you must use Windows' built-in character map or type the appropriate American Standard Code for Information Interchange (ASCII) code on the numeric keypad.

DYNAMIC PAGE — HIGHEST POSSIBLE CLASSIFICATION IS TOP SECRET // SI / TK // REL TO USA AUS CAN GBR NZL (U) Ask Raul: Numeric Character Reference FROM: ‘Raul’, a DNI Analyst Unknown Run Date ...

As shown in the screenshots below, you can also use a custom numeric code if you don’t want to use an alphanumeric one. Read more about passcodes on iOS devices in Apple’s support document here.