The PGP Universal Server Whole Disk Recovery Token (WDRT) string is encoded using a system called Base32. The character set of Base32 is case-insensitive and allows you to simply enter the WDRT.
Whole Disk Recovery Token strings contain both letters and numerals. Because it can be difficult to tell the difference between certain letters and numerals, Whole Disk Recovery Tokens use letter and numeral equivalencies. You can type either letter or numeral when you use a Whole Disk Recovery Token, and the token string will be accepted. The following are interchangeable:
Letter B and numeral eight (8)
Letter O and numeral zero (0)
Letter I and numeral one (1)
Letter S and numeral five (5)
For more information regarding Base32, please see the following external link.