I always give a range with my estimates. The range is due to risks like current unknowns, probability of bugs due to interaction with other components, additio

I always give a range with my estimates. The range is due to risks like current unknowns, probability of bugs due to interaction with other components, additional work that will possibly need to be done, documentation complexity, technical debt in related pieces etc. Sometimes those can be rather extreme so my estimates have been "one month, plus/minus three months". If four months is acceptable then everyone is happy and as progress is made the range narrows. If time is tight then the discussion turns to reducing the range which puts everyone on the same page.