How many keys does this product come with? I only need to protect one laptop,but last Jan. when I purchased my subscription it came with 3 keys.After the initial download I had two left.When I downloaded Windows 10 in Aug.2015 it disabled my Norton Security and I was instructed to use one of the two remaining keys left to arm my laptop with the Norton product I had purchased.I need to renew my security and I want to make sure I have more than one key in case I ever need to use another key for situations like the windows 10 download.Without that extra key I would have been forced to buy another whole subscription.Thank You for any help.