Why do some blow one extra candle for good luck on their birthdays?

The other day in my Japanese 2 class, we were discussing birthdays I believe.
Well the majority of my class says they blow one extra candle for good luck. My teacher, a few other students, including I myself have never heard of such a thing.
Do you guys know anybody that does that? Do you do it yourself?
Where has this originated, and why do you think one extra candle blown is good luck?
I think my teacher says we get extra credit if we find out and tell him :D