[exchange guide] Add more explicit native token docs (#655)

apps/nextra/pages/en/build/guides/exchanges.mdx

@@ -73,6 +73,11 @@ We will call this from now on **migrated coins**. Migrated coins can be used int
 with Fungible Asset and Coin standards.  This is important to note when querying balances, to
 use coin functions and not fungible asset functions.
 
+<Callout type="info">
+APT, the native token of Aptos, is a migrated coin.  This means it can be used
+with both the Coin and Fungible Asset standards.
+</Callout>
+
 ### Coin Standard (tl;dr)
 
 A **coin** has an associated contract that holds the on-chain struct that represents the coin.  The coin is
@@ -111,7 +116,8 @@ returns a balance of `100000000`, this is `1 APT`.  If it returns `100` this is
 
 <Callout type="info">
   Note: This includes APT and any other coin that was migrated to a fungible
-  asset.
+  asset.  If the asset is a migrated coin, use this over fungible asset balance.  The
+  fungible asset balance will not include the coin portion of the balance.
 </Callout>
 
 To retrieve the balance of a coin, or a coin that was migrated to a fungible asset, you can use
@@ -1112,6 +1118,11 @@ Here is an example of a migrated coin with APT: https://api.mainnet.aptoslabs.co
 
 ### Coin (or migrated coin) Transfers
 
+<Callout type="info">
+  APT, the native token of Aptos, is a migrated coin.  Please use the `aptos_account::transfer` functions
+  to transfer APT tokens.
+</Callout>
+
 We suggest you use `0x1::aptos_account::transfer_coins<CoinType>(receiver address, amount)` for transferring coins.  It will
 register the coin if it hasn't been registered yet, and create the associated account if it hasn't been created yet.
 This will continue to work with any coins that were migrated to a fungible asset, including APT.