These numbers give an idea of the value of the windows and doors to the followings tests:
A= Air, the scale is from 1 to 3.
B= Water penetration, the scale is from 1 to 7.
C= Wind load resistance (The capacity of a window or a door to withstand hurricane or extreme winds.), the scale is from 1 to 5.
These tests must be passed in an accredited laboratory and are essential to obtain an acceptation number from the CCMC, Canadian Construction Materials Centre.
An important point to verify when buying windows and doors is to be sure that it is the manufacturer itself (and not the PVC extruder) that went through the testing process. That is a way to be sure that the window or door you're buying will be identical to the one that has been tested.
For a couple of years, Fenplast does some testing on brand new products randomly taken from the production line, just to make sure that the "regular" one will be as efficient as the one being tested.