Some tasks have a high degree of uncertainty. Others don't.
Back when I was using a ruby-on-rails style framework (in PHP) I would frequently get 20 hours of work estimated properly down to 15 minutes when it came to adding simple features to a web application.
If on the other hand you are trying to figure out the gap between what the documentation says should work and what actually works, that is hard to estimate.
Some tasks have a high degree of uncertainty. Others don't.
Back when I was using a ruby-on-rails style framework (in PHP) I would frequently get 20 hours of work estimated properly down to 15 minutes when it came to adding simple features to a web application.
If on the other hand you are trying to figure out the gap between what the documentation says should work and what actually works, that is hard to estimate.