You now have the ability to offer more Custom Fields in your system.
You have a few options here:
1. Leave it at 20.
2. Increase the number to 30.
3. Increase the number to 40.
More is not necessarily better. The configuration screens and Contact Card can get a bit overwhelming the more Custom Fields you have.
I recommend you select the minimum needed for your users. You can always upgrade later.
Please note that your selection will apply to all Groups and all Users, so choose wisely!
Let me know how you want to proceed and I will make the adjustment for you.