Fabric Custom SQL Pools

Hello all, Since the changes in CU-charges regarding Fabric, I've experimented a bit to reduce the existing load on our capacity. One things that was mentioned here a couple of times were the SQL Pools. I've set this up for some tenants / workspaces and I noticed a significant decrease (up to 10% of Power BI usage), based on following settings. But to completely honest, I have no clue what the % mean. I see no impact on refresh duration, performance,... I only saw the CU drop after this change. I won't know if there is an impact increasing this to 10%, 50%,... Anyone has some knowledge around