Do you include a letter as part of the last 4 digits in passport number?

Good day to all. I would like to ask if you included the letter in your passport number when you registered for the CFA Level 1 exam. My passport number has a letter at the end, and I am a little hesitant to include it as my last 4 digits of passport number. Please inform me if you have the same case as mine. Thank you very much.