These extensions are based upon external relationships among waves 1,3 and 5. Length of waves are added on top of each other. W3 could be equal to or 1.618 of W1, when added on top of W1. In this case W5 would be extended. But if W3 is more than 1.618 of W1 then W5 would be shorter than W3.
In case of extension, W5 could be equal to 1.618 times the length from 0...
