I have never seen this used and the construction makes no logical sense. Lots of people (including me) make common grammar and usage errors but that doesn't make them legit. Can you provide another example from an edited source or an entry in a style guide? I just Googled around a bit and saw nothing to support this. I looked at 3 different discussions on the date abbreviation apostrophe and they all revolved around which way the "tail" of the apostrophe should point (it's to the left) but NO ONE put the apostrophe on the right of the numerals. That is just plain wrong.
I agree, makes no sense to me at all. I guess my most common 'source' is others' powerpoint presentations. As a marketing professional I have built thousands of these, collaborated with others on thousands more, and seen even more that I wasn't involved in creating. I finally got tired of correcting this particular 'error', and concluded it is so common it should just be considered a colloquialism instead of an 'error' (The younger President Bush realized his "nucular" pronunciation of the word "nuclear" was technically incorrect, but made no effort to change the way he pronounced it, claiming it was a "regional colloquialism"). (Not that "W" is my grammar role model, but "access" didn't used to be a verb, nor did "google", however that usage is commonly accepted for both due to everyone doing it.)
Maybe Kib should weigh in on this.