fix(docs): fix FAssets formula and explanation (#886)

Author: fassko

docs/fassets/3-redemption.mdx

@@ -34,7 +34,7 @@ This is the summary of the redemption process:
 
 4. Every agent pays the redeemer on the underlying chain and includes the payment reference in the memo field of the payment transaction.
 
-   Agents can pay the redemption from any address they control on the underlying chain.
+   Agents can pay the redemption from their own address they control on the underlying chain.
    It does not need to be the same address where they receive minting payments.
 
 5. After the payment is finalized, the agent uses the [FDC](/fdc/overview) to prove the payment and obtain a payment proof.

docs/fassets/4-collateral.mdx

@@ -213,21 +213,21 @@ It is worth noting that:
 <details>
 <summary>Fee entitlement formulae and examples.</summary>
 
-The following formulas consider all the above information to calculate each provider's due share of FAsset minting fees.
+The following formulas are based on the concept of virtual fees, which are the fees that a provider would be entitled to if they had no fee debt.
 
 The amount of debt a provider $p$ is assigned upon entering a pool is calculated as:
 
 $$
-fee\_debt_p = { added\_collateral_p \over collateral\_in\_pool } \times fees\_in\_pool
+fee\_debt_p = { added\_collateral_p \over collateral\_in\_pool } \times total\_virtual\_fees
 $$
 
 where:
 
 - $added\_collateral_p$ is the amount of FLR tokens that provider $p$ is adding to the pool.
 - $collateral\_in\_pool$ is the amount of FLR tokens in the pool before adding the new tokens.
-- $fees\_in\_pool$ is the amount of FAsset minting fees currently in the pool.
+- $total\_virtual\_fees$ is the sum of all provider's virtual fees.
 
-The following formulas are based on the concept of **virtual fees**, which are the fees that a provider would be entitled to if they had no fee debt.
+The following formulas use **total virtual fees**, which are the gross fees accrued to a provider assuming no prior fee withdrawals, slashing, or outstanding fee debt.
 
 The **total virtual fees** is the sum of all provider's virtual fees and can be expressed as:
 
@@ -269,7 +269,7 @@ The following example shows fee entitlement.
 | An agent creates a new vault.                                         |           0 |            0 |              0 |                  0 |
 | Alice deposits 100 FLR and gets 100 CPTs in return.                   |     **100** |            0 |              0 |                  0 |
 | 10 FAssets of fees are added to the pool due to a mint.               |         100 |       **10** |              0 |             **10** |
-| Bob deposits 100 FLR and gets 100s CPT in return.                     |     **200** |           10 |         **10** |             **20** |
+| Bob deposits 100 FLR and gets 100 CPTs in return.                     |     **200** |           10 |         **10** |             **20** |
 | 10 more FAssets of fees are added to the pool due to another mint.    |         200 |       **20** |             10 |             **30** |
 | Alice withdraws 10 FAssets of fees.                                   |         200 |       **10** |         **20** |                 30 |
 | Bob exits the pool by returning the 100 CPTs and withdrawing 100 FLR. |     **100** |        **5** |         **10** |             **15** |