Cancellation Indemnity

Hi, just wanted some clarification on how the cancellation indemnity works. Tried to search site and message board but not clear to me.

So as an example choosing a high end cell phone such as Samsung Galaxy S8

http://www.videotron.com/residential/mobile/devices-and-accessories/phones/galaxy-s8#/order/info

It lists $1029.95 as cash price

$249.95 as cost for a 24M plan at $79.95

$149.95 as cost for a 24M plan at $89.95

Assuming I had signed the 24 month contract and asked Videotron to cancel early, how is cancellation fee calculated?