Hi,
If, at the time of submission you had 3 years of experience, then your reference letters should show this clearly. In this case, and though you mention 2 yrs or more, it won't harm, and the VO should capture this, nonetheless I suggest you write a letter to explain this error.
However, if you claim that now and after you submit your app that you cross the three year experience, then, I'm afraid you can not claim the extra two points.
It depends on which scenario you are in.
Cheers
Mezo