300 LOC in 10 minutes. Or 2 sec per loc. Or for average 30 char line, 600wpm reading speed.

OK.

There is little you can review properly in 10 minutes unless you were already pairing on it. You might have time to look for really bad production-breaking red flags maybe.

Remember the underlying reasons for PR. Balance between get shit done and operational, quality and tech debt concerns. Depending on what your team needs you can choose anything from no review at all to 3x time reviewing than coding. What is right depends on your situation. PR is a tool.