Question regarding indexes

[pooptarts92]

Ok so let's say we're talking 15 vs a 10 in a LS game. In my book in the surrender section it says 0 for surrender. Does this mean surrender at count of 0 and higher, or DO NOT surrender at counts of 0 and lower? I know it's probably a marginal play, but every bit counts. My main focus is right at the neutral count point, is this a surrender or hit?
It's the same with soft 19 vs a 6, it says 0. So do or do not double at 0?

 

[Sucker]

In regard to the first question; surrender at 0 or higher. As the count goes up, two things happen: The dealer has an increased chance of having the 20, and your chance of busting your 15 goes up.

It's the same thing with the 2nd question (and with ALL double downs,for that matter). Double at zero or higher. The higher the count, the greater the chance of the dealer busting.