Thanks for suggesting a reasonable timeline! The hotel did state that their computers have been acting up, although reviews for this hotel mention that overcharging is an ongoing issue.

I definitely have proof (flights, booking info) that I didn’t stay 6 nights, but it looks like they charged me twice for the 4th night. Not sure how to prove that I didn’t need 2 rooms that night, except for witness statements from my partner (staying with me in my one room) and boss (also staying in hotel).