OK, the smaller sizes of the North Daytona (5.4 m2 and 6.0 m2) have an adjustable head strap at the top.
So, you adjust the strap and headcap so the mast extends beyond the top of the sail (approx. 20 cm on the 5.4 m2 Daytona and approx. 5 cm on the 6.0 m2 Daytona).
Check out this link to the NS Daytona:
Follow the links to the little Hexagon with the "2 masts fit all" which explains the use of the "Carbon extendo" extension for the larger Daytona sails.
BUT, take note of the mast bend specifications in the chart for the Daytona sails.
The best mast for the 5.4 m2 Daytona is a 430 cm MCS 21-23.
So to get the best perfromance from the smallest Daytona, you need a 430 mast, and to get the best perfromance from mid size Daytonas you need a 460 IMCS 24-26 mast, and for the the larger Daytonas, you need a 490 mast and then the 490 mast with the CX (carbon extender) for the 10.0 m2.
So, what they are telling you is that you can get away with only 2 masts + the Carbon Extender (a 460 and a 490 to cover the entire range 5.4-10.0 m2) of Daytonas, but if you really want the full performance you will need 3 or 4 masts.
Hope this helps,