When I use wikitree +, searching for Capital letter III with Suggestion 761, it does not show that profile. You have marked it as a False Suggestion, but what you have in there is not a normal capital I.
I see plenty of other profiles that have the III. Look at Gilbert-8 that has the III in the suffix, which has no Suggestion, but it looks different than your profile Suffix Field Ⅲ
Edit - looking at the message in Edit mode, the capital letter for I looks different than it does when you are viewing it. In Edit mode, it doesn't have the bars on the top and bottom, but when viewed, it does.
Best idea is to remove everything from the suffix field, go to another field, then go back to suffix and use your capital letter I for the suffix field.