Delete, Substitute, Keep
To effectively summarise, you must delete some information, substitute some information and keep some information.
Delete information that is not valuable to you or does not suit your purpose or does not address your purpose for reading.
Substitute words that are more natural everyday words making the overall meaning easier to recall and understand.
Keep the words and passages that convey the overall meaning of the information.
When you copy information word-for-word, you leave no capacity in your working memory for analytical thinking. Note-taking in your own words helps you to identify what is important and why it is or isn't important.