Fade In/Out Audio are very deliberate filters. They are sloped from start to end as you set.
Example: Start of Fade In Audio volume is 0. End of the Fade In Audio volume is 100%.
You might want to use the Gain/Volume filter instead. This filter allows you to use Keyframes to get exactly the fade you want.
Example of Gain/Volume filter with 3 Keyframes. Keyframe Type: Smooth
It will take some practice to find the correct Keyframes s
Keyframes Video Tutorial: