The Additional or extension class can only be purchased if you have previously completed a FCC canoe or kayak class and your course coach has let you know that addtional classes are available.
You need to tell us
1/ The dates of the previous course that you attended
2/ The name of your coach
3/ The date of the extra class ie the extra class that you are paying for.
Nb: you can only purchase the 'Extra class' if you been advised by your coach that a 'Extra class' is available.
Note also: you need to purchase each day of extra classes separately - ie add each separate day to the cart before checking out.