Read the back of the card - it spells out the terms of the discount. It shows "Discounts applicable on purchases up to: $2700"
I used one this spring and when I put the code in at the time of order it showed total discount allowed was $2700 - meaning you would have to spend a total of $10,800 to use the full discount amount.
It's actually better than expected - I initially thought if the total you spent was more than $2700 it wouldn't work.