How to read time estimates: Whenever anybody says something will take, say, 5-10 hours what they mean is:

“My most optimistic estimate is 10 hours, but that sounds excessively long; if I add an interval people will mentally think it’s really just 5 hours yet I will technically still be truthful if I finish in 10.”

The 10 hours optimistic estimate is of course the result of a subconscious internal discussion where our more realistic estimate is passed in the same manner from our brain to our mouth.