The way i’ve always done it is after you add your standard fade in/out, you can double click the top corner of the region and a fade editor will come up. In the top right corner of that window there is a section that you can adjust the standard fade (Photo Attached). It should say 0.0.0.20 in your situation, just change the 20 to how ever many frames you want for your standard fade. After that you can repeat with the other end of the region.
