-e) coupled with an extended factor no spaces are allowed in-between, i.e. -e8 is ok, while -e 8 is incorrectExtended mode
The extended mode adds a second contact sheet after the default contact sheet composed of smaller captures.
A suggested usage of this mode is using the main contact sheet as a quality preview (showing the image quality) and the extended contact sheet as a content preview (showing what's in the video).
The extended mode is enabled by the -e (--extended) option. It has an optional argument 1), the extended factor, which by default is 4 (so -e and -e4 are equivalent).
Captures in the extended contact sheet will be 1/4 the size of normal captures (half width and half height).
The extended factor is used to determine the number of captures in the extended sheet: The resulting number will be the number of main captures times the extended factor, rounded to the next even number. Confusing I know 
Examples
$ vcs -n2 -e: 2 captures, 8 extended captures (2×4)$ vcs -n1 -e8: 1 capture, 8 extended captures (1×8)$ vcs -n1 -e9: 1 capture, 10 extended captures (1×9=9, next even number: 10)
1)
Note that due to technical limitations, when using the short option form (