On the web, head to the holdings page and click the button to withdraw from your USD wallet. Verify your linked bank account, choose your amount and click the button to deposit the funds into your bank.
Staking rewards are often given out in percentages instead of fixed figures. So, the more you stake, the more rewards you earn. For example, an 8% APY for 50,000 staked SOL is 4,000 SOL, while the same 8% rate is 4 SOL if you stake only 50 tokens.