Confused by this comment in the Los Angeles BB Murder cases.

Maybe I'm just being really obtuse right now but I don't understand what Mello it getting at here, but mainly the last sentence:

'Depending on how you look at it, this might have been a good thing for the world even the murderer Kira, had he known just how deep Misora's connection with L was, would never have killed her so quickly. L's life was only extended by a few extra years, but even that may well be thanks to Misora… nah, not even worth speculating about.'

I looked it up and L didn't even live a full year longer than Misora. So Misora not knowing she met L, meaning Light could never have foud out that she met L either, only might have extended L's life by like 10 months not 'a few extra years'.

Please don't comment any spoilers for the rest of the book, as I've only made it up to this line. (If the answer is a spoiler i'll just keep reading and find out, but I doubt it is).