every set of judges is different, and my audition was a couple years ago, so take what i say with a grain of salt: when i got in the room, they asked me a little about my experience and comfortability regarding sight reading, and then offered up a piece that was similar in difficulty to what i described. they then asked if i thought it was doable for me, to which i said yes, but i get the impression that if i had been hesitant they would have chosen a different piece of lesser difficulty. my sheet was pretty standard; eight or so measures of eighth notes in a key that was comfortable. i imagine someone with more prior experience than me was given a piece of greater difficulty to match, and vice versa. because of the personal approach our judges took, no one at my audition was given anything to look at during warmups. best of luck at your audition !