The number of lines of code in a pull request is incredibly important for the code review process.

According to a SmartBear study for of a Cisco systems team, teams should only review 200-400 lines of code per pull request. In that span, a reviewer can find 60-90% of the defects that are present in the code.

Source: https://smartbear.com/learn/code-review/best-practices-for-peer-code-review/