add parenthetical about optional Owner field

Author: DennisDawson

docs/concepts/tokens/nfts/dynamic-nfts.md

@@ -15,7 +15,7 @@ When minting a new NFT, set the `tfMutable` flag (`0x00000010`) to enable the ab
 
 ## Modifying a dNFT
 
-Use the `NFTokenModify` transaction to update the URI field of a dNFT. Provide the `Account` of the issuer or an authorized minter, the `Owner` of the dNFT, the `NFTokenID`, and the `URI` to the new object data.
+Use the `NFTokenModify` transaction to update the URI field of a dNFT. Provide the `Account` of the issuer or an authorized minter, the `Owner` of the dNFT (if different than the `Account` address), the `NFTokenID`, and the `URI` to the new object data.
 
 ### Sample NFTokenModify Transaction
 
@@ -29,4 +29,4 @@ Use the `NFTokenModify` transaction to update the URI field of a dNFT. Provide t
   "NFTokenID": “0008C350C182B4F213B82CCFA4C6F59AD76F0AFCFBDF04D5A048C0A300000007",
   "URI": "697066733A2F2F62616679626569636D6E73347A736F6C686C6976346C746D6E356B697062776373637134616C70736D6C6179696970666B73746B736D3472746B652F5665742E706E67",
   }
-```
+```