Apply suggestions from code review

Co-authored-by: Hadrien Croubois <[email protected]>

ERCS/erc-7674.md

@@ -31,9 +31,9 @@ Call to `transientApprove(spender, value)` allows `spender` to withdraw within t
 
 Compliant contracts MUST use the transient storage `EIP-1153` to keep the temporary allowance. For each `owner` and `spender`, the slot MUST be uniquely selected to avoid slot collision. Each slot index SHOULD be derived from the base slot index for transient allowances, `owner` and `spender` addresses. Slot MAY be derived as `keccak256(spender . keccak256(owner . p))` where `.` is concatenation and `p` is `keccak256` from the string uniquely defining transient allowances in the namespace of the implementing contract.
 
-Compliant contracts MUST add a transient allowance check to the `transferFrom` function. The permanent allowance can only be spent after the temporary allowance has been exhausted.
+Compliant contracts MUST add a transient allowance check to the `transferFrom` function. The permanent allowance SHOULD only be spent after the temporary allowance has been exhausted.
 
-Compliant contracts MUST add a transient allowance to the permanent one when returning the allowed amount to spend in the `allowance` function.
+Compliant contracts MUST add a transient allowance to the permanent one when returning the allowed amount to spend in the `allowance` function. In case the sum of the transient and permanent allowance overflow, `type(uint256).max` MUST be returned.
 
 ## Rationale