For the integrated essay, you first read a short passage for 3 minutes, then you listen to a lecture on the same topic. Then you must summarize both, showing how the lecture "casts doubt on [argues against]" the reading.
When writing your summary (you have 20 minutes), you will see the reading passage on your computer screen. However, you cannot replay the lecture. You will hear it only once. Therefore, good notes are critical (this is very much a note-taking task, one that tests automaticity - see note-taking strategies).
The raters will rate this task holistically (see rating holistically). So ETS says. In reality, the raters will focus more on the lecture summary. Why? Because a proficient lecture summary is more challenging. Why? Because it depends on good notes. Good writing, in turn, depends on good notes, which rely on proficient listening comprehension. In short, good notes means a higher score.
Why do the raters focus less on the reading summary? Because the reading passage will be on the computer screen as you write. That makes things much easier. The raters know this. They also know that test-takers spend a lot of time summarizing the reading because it is on the computer screen. The result is test-takers often have long reading summaries. Very long. Remember: Long doesn't always mean proficient.
It goes without saying that a proficient integrated essay (a high-scoring integrated essay) proficiently summarizes both the reading and the lecture. Don't fall into the trap of spending more time summarizing the reading. The money is in the lecture.
The Pro