$7/mo * 12 * 80% * 80% = $53.76 with the discounts. Price of 8 months without the discounts is $56.
If you pay for 8 months today, you'll be good for the next 18 months. It's a stretch, but not really wrong.
$7/mo * (12 - 2) * 80% = $56.00
$7/mo * 12 * 80% * 80% = $53.76 with the discounts. Price of 8 months without the discounts is $56.