I think it means bend the string until it sounds like your fretting it(the number in the bracket)... Memorize the fretting before you begin to play it up to speed and it helps alot.
dude....the hell song....youre a noob....damn, i respect you
the number in the bracket is the pitch you're supposed to bend the previous number up to. ez terms: 13 (15) = 13th fret bend up until it sounds like ur 15th fret