He may be asking about what you did in the past, but what he actually will want to clarify is what you can do for the company now ( Based on your experience and achievement, it is like- if you did it once, you can do it again).
That is why he may ask you to provide specific examples.
Therefore, talk about past accomplishments in a way that shows relevancy to the specific job for which you are applying and interviewing.
Study the job description carefully. Note the requirements and qualification they listed. You’ll want to target these as much as possible when developing your answer.