Normally, memories are impossible to alter. However, if those memories have been artificially recorded into something, altering them becomes very simple, especially when a person is deeply immersed in those memories.
Because the Petrifying Potion had long since been brewed, the fact that the monster emerging from the Chamber of Secrets was a Basilisk had also been revealed long ago. This forced Voldemort to slightly modify the memory when showing it to Harry, resulting in the details clashing when the two sides conversed and not matching up.
Realizing that things did not add up, Harry instantly understood that the diary was problematic. Therefore, after getting the information he wanted, Harry immediately said his goodbyes and prepared to leave. After all, the surrounding Acromantulas were already closing in, and if they did not run now, they would be completely surrounded.
Chapter 112