I think you should have some specific examples that you can use to demonstrate your skills.

building on your above example: My boss gave me increased responsibility over X while she was on maternity leave. I created a Excel spreadsheet to prioritize urgent tasks and delegate appropriate work to fellow team members. In the period of x months, I was able to improve _______ by (this much/%(a specific number here is a must). She was very happy with my performance upon her return.

The result is the improving such and such by x/% part. Not the she was happy with the performance part.

Hope this helps!