I've read other pages saying the witnesses want 5 million in HBD savings.
The witnesses cant set what will be the amount in the savings it is up to users how much they will put in. Leofinance put a goal of their own to have 5M in HBD liquidity in their USDC-pHBD pool on Polycub. This is totally different from HBD in savings.
The 20% interest on 5 million HBD will create 1 million of debt in the first year.
Yes, at the moment there is around 3M HBD in savings. For context ... at the moment there is around 26M HIVE equivalent printed per year, or around 2.2M per month ...