Writing a summary is an important academic skill. The strict word limit of a summary makes it necessary to make selections and decisions which require a thorough knowledge and understanding of the topic at hand: Only the most important and relevant aspects of the talk will be represented in the summary, and the summary's author first has to identify those. As a consequence, it requires more reflection and a deeper understanding to write 200 words than to write 1000.
In addition, the length constraint forces the author to think carefully about the words used and the grammatical structures employed. Unreflected writing wastes words and makes it difficult to complete the task effectively.
Example 1. "To argue his point, Smith gave a very detailed example of Shakespeare's characteristic humour. In this example, he stressed particularly the effect of wordplay and allusion." (26 words) --- "To argue his point, Smith gave an example of Shakespeare's humour stressing the effect of wordplay and allusion." (18 words)
Example 2. "There were many completely innovative proposals that were submitted to the committee." (12 words) --- "The committee reviewed many innovative designs." (6 words)
Example 3. "It is clearly the case that the information-based economy demands employees who know how to learn logic applications." (19 words) --- "The new information-based economy demands employees who can learn logic applications." (12 words)
Example 4. "The report of the committee was comprised of a list of essential skills needed by graduates of the Logic Programme." (21 words) --- "The committee's report listed essential skills for the Logic Programme graduates." (11 words)
If you want to know more about writing summaries, you could try