1. The Ev line is measuring your
expected value at the point that you're all in for a pot, based on the statistical probably that your hand will win. So, if you're an 80% favorite in a $10 pot and you're all in (or all other players still in the pot are all in), your expected value is $8. Your actual line reflects what you actually made - if you won the pot, you won $10, if you lost, you won $0. If your Ev line is above your actual winnings line, it means you got sucked out on in some pot. It's basically a measure of how lucky/unlucky you're running.
There are a number of threads that talk about this line here on the forum, search if you're really interested, but (I think, not trying to speak for everyone) most forum regulars here see this as relatively trivial - note from the example provided it's impossible to win exactly the Ev of $8, you're always either going to hold up as the 80% favorite (so you "sucked out" for the extra $2 as well as winning the Ev) or you'll get sucked out on. I think Zachvac has a detailed series of posts describing this.
2. Non-showdown being negative simply says that when you have money in a pot and you don't go all the way to showdown, you're losing money. Different styles will produce different kinds of lines. Extremely passive postflop play, where lots of hands are folded before showdown, combined with loose preflop play, will result in nsd being hugely negative, as an example (not suggesting that your play is an example).
I'm guessing this isn't a huge leak in your game if you're relatively close to flat - my nsd line is a good deal more negative, you can see it here, it's post #95 in this thread, including some good feedback from good regs in the subsequent posts -
https://www.cardschat.com/forum/lea...ro-grinder-thread-2nl-25nl-150754/index3.html
