There are several things wrong in your searches. First you used the search string "classification 715/234" in google patents. Since google searching is very clever it is not easy to know what it thinks you are looking for but it is not at confined to patents in that class. It will presumably hit on anything with the word classification and the characters 715/234. That text could appear in cross-referenced classes or on a list of citied patents as the classification they were found in. It could be part of a phone number. To constrain google patents to a particular US classification one would use google patents advanced. It would create a search string "uspclass:"715/234". You can also constrain google patents by office and by status (application or issued patent).
Regarding the report, I may have missed it but I don't see it going into subclasses. It has a total of 17,179 from 1977 to 2012 for all subclasses within the major class 715.
The patent office search site is a good way to look up this type of information and it looks like you correctly used the search string ccl/715/234. Since the USPTO searching is completely separate between applications and issued patents your search would have showed only patents. To add in application publications you use the same search string on a different USPTO URL.
I do not know your purpose in this search but adding the application to the issued patents will double count some but not all cases. Any application that was published that resulted in an issued patent will be in both counts. Any patent that came from an application that was not published (none were published until a couple of decades go and sone are not published now by applicant request) would be a patent but not an application.
