staking/user-guide.md: update faq

docs/bnb-smart-chain/staking/user-guide.md

@@ -64,14 +64,74 @@ After the unbonding period, you can claim your stakes by clicking the `Claim` bu
 
 ## FAQs
 
-### Which wallet can be used to delegate to validators?
+### Q1: Which wallet can be used to delegate to validators?
 
 Currently, `MetaMask` and `TrustWallet` are supported, along with any wallets compatible
 with `WalletConnect`.
 
-### Can I delegate/undelegate/redelegate/claim stakes on explorers?
+### Q2: Can I delegate/undelegate/redelegate/claim stakes on explorers?
 
 If you want to do the aforementioned delegate/undelegate/redelegate/claim operations on BscScan or BscTrace, 
 you should call the staking hub contract in the following URLs:
 * [BscScan Stake Hub](https://bscscan.com/address/0x0000000000000000000000000000000000002002#writeContract)
 * [BscTrace Stake Hub](https://bsctrace.com/address/0x0000000000000000000000000000000000002002?tab=Contract&p=1&view=contract_write)
+
+### Q3: What is staking credit (stBNB)?
+
+When you delegate BNB to a validator, you receive **staking credit tokens** as proof of your stake. Each validator issues its own unique credit token:
+
+**Token Naming:**
+- Name: `Stake{{validator moniker}}Credit`
+- Symbol: `st{{validator moniker}}`
+- Example: Staking with "BNB48Club" → receive "stBNB48Club"
+
+**Key Properties:**
+
+- ✅ Represents your staked BNB + accumulated rewards
+- ✅ Auto-compounding: value increases as validators earn rewards
+- ✅ Rewards automatically distributed when you undelegate
+- ❌ Non-transferable between addresses and each validator's credit is unique
+
+### Q4: How to calculate my staking balance?
+
+Your staking credit value in BNB can be calculated using:
+
+```
+Your BNB Value = (stCreditAmount × totalPooledBNB) ÷ totalSupply()
+```
+
+**Where:**
+
+- `stCreditAmount`: Your staking credit balance
+- `totalPooledBNB`: Total BNB in validator's pool (stakes + rewards)
+- `totalSupply()`: Total supply of the validator's staking credit
+
+**Example:**
+
+| Time | totalPooledBNB | totalSupply | Your stCredit | Your Value | Profit |
+|------|----------------|-------------|---------------|------------|--------|
+| Day 1 | 10,000 BNB | 10,000 | 100 | 100 BNB | - |
+| Day 30 | 11,000 BNB | 10,000 | 100 | **110 BNB** | +10 BNB (10%) |
+
+Your staking credit automatically appreciates as the validator earns block rewards!
+
+### Q5: How to query total pooled BNB programmatically?
+
+Use this JavaScript example to query a validator's total pooled BNB:
+
+```javascript
+import { ethers } from 'ethers';
+
+const provider = new ethers.JsonRpcProvider('https://bsc-dataseed.binance.org');
+const OPERATOR = '0x...'; // validator operator address
+
+const hub = new ethers.Contract('0x0000000000000000000000000000000000002002',
+  ['function getValidatorCreditContract(address) view returns (address)'], provider);
+
+const creditAddr = await hub.getValidatorCreditContract(OPERATOR);
+const credit = new ethers.Contract(creditAddr,
+  ['function getPooledBNB(address) view returns (uint256)'], provider);
+
+const bnb = await credit.getPooledBNB(OPERATOR);
+console.log('Pooled BNB:', ethers.formatEther(bnb));
+```