fix: address amount defined in invoice and request

05.md

@@ -32,7 +32,7 @@ The wallet `Alice` includes the following `PostMeltQuoteBolt11Request` data in i
 }
 ```
 
-Here, `request` is the bolt11 Lightning invoice to be paid and `unit` is the unit the wallet would like to pay with. `amount` is the amount to be paid if the invoice does not have a defined amount.
+Here, `request` is the bolt11 Lightning invoice to be paid and `unit` is the unit the wallet would like to pay with. `amount` is an integer or null, representing the amount to be paid. If the invoice already defines an amount, the amount in the PostMeltQuoteBolt11Request **MUST** match the amount in the invoice exactly.
 
 The mint `Bob` then responds with a `PostMeltQuoteBolt11Response`: