By definition, an Add-On is an addition to your current contract, which already defines the use year month. If you get a different use year, then it's not an add-on, but rather a brand new Master Contract purchase.
October is still in UY 2007. Normally with an add-on purchase you will receive current year points, so you would get Oct 2007 points. The exception would be AKV if buying into Kidani. Since those buildings aren't open yet, you would not be eligible for points until they were ready for occupancy. If that was after Oct 1st, then you would start off with 2008 points and not 2007 points.
The size of the contract makes no difference. You will get Oct 2008 points regardless whether you get Oct 2007 points or not.
Again under special circumstances for AKV purchases, you may not be able to use your points until a specific date. You might wonder why. Why not use them at OKW for example. The reason is that you are taking space at OKW from an OKW owner, but that OKW owner is not able to use their points, in exchange, at your AKV resort since it's not open yet. That's why some AKV points cannot be used until after a specified date.
Hope that's not too complicated.