What is the difference between 3 years and more than 3 years? Lets examine by some examples.
3 years + 1 day is more than 3 years
3 years + 29 days is more than 3 years
3 years + 2 months is more than 3 years
3 years + 1 years is more than 3 years
3 years + 20 years is more than 3 years
3 years + 1 million light years is more than 3 years
If you know the exact date since that person has known you, then you can add 3 years to that date, and one day after that he can give you a reference. Any date after doing the above calculation is included in "more than" 3 years. (Please note its "more" not "less"). So every since day, every hour, every minute, every second that passed after the 3 years period is included in "more" than 3 years
Please also see
http://dictionary.reference.com/browse/more?s=t