Let's say that you've added an adoption rate to your benefit of 25% for year 1, 50% for year 2, 75% for year 3 and 100% for year 4 (using the Benefit Modifiers functionality), when you look at the cash profile for that benefit the cashflow graph mimics a step:
If you want this to be reflected as a more gradual increase you can use the Benefit Smoothing functionality: