Adding IME to Super Visa through IRCC portal

[Socho]

Going to try to resubmit through the new portal but when I try to add my IME number to the medical portion, I keep getting an error:

Error:
UMI number should be either 2 characters followed by 8 digits (AA99999999), 2 characters followed by 9 digits (AA999999999) or 'U' followed by 9 digits (U999999999).

Which is odd because the instructions state:

Have you had a medical exam performed by an IRCC authorized panel physician (doctor) within the last 12 months? (required)Yes/No
If known, please provide your Immigration medical examination (IME) or Unique medical identifier (UMI) number. (optional)The number can be found on the eMedical Information Sheet or the IMM 1017B form. You can get a copy of either document from the Panel Physician who examined you.

How did people add their IME??