The Verbal Reasoning and Quantitative Reasoning sections are section-level adaptive. The first operational section of each measure (i.e., Verbal and Quantitative) is of average difficulty. The difficulty level of the second section of each of the measures depends on your overall performance on the first section of that measure.
For example, if for the Quantitative measure, you do very well on the first quant section, the second section of the Quant will be at a higher level of difficulty. If you have not done well in the first section, the second section might be easier or similar.
The computer selects the second operational section of a measure based on your performance in the first section.