It's likely a copy-n-paste style error, which since I was the first editing line of defense on that book, puts a share of the blame on me, but the "per rank" logic doesn't jibe with the rest of the context.
If you read all the associated rules text for that option, can you apply them to ranks, or does trying to use that table note seem to conflict with the rest of the text?
As an example, if you purchased 42 ranks of Body development by level 20, of a profession that gets +1 for BD, would you then get +42 hits? But if you purchased 10 ranks by level 20 you'd get +10, but then get none after level 20? (Since +1 bonuses become +0 after level 20?). You'd need to add on some more rules to make the note work, and when confronted with fixing a table note vs re-writing the whole section of the rules, I lean toward assuming the table note is incorrect and the body text is correct.
Without any of the other supporting rules and restrictions making any reference to ranks there doesn't seem to be any clear way to integrate that table note with any of the rest of the text, so my gut call would be to stick with the general rules text and the context of all the other table notes referencing levels.