Box 7 on 1099 R calls for two codes, a number and a letter. Turbo tax says the letter code is wrong from Edward Jones

Form 1099-R box 7 uses a single number or letter for the code in box 7.  This link What do all the codes in Box 7 of the 1099-R mean? list all of the codes for box 7 Form 1099-R  and what they are used for.