Another lsfTransferable definition

content/references/protocol-reference/data-types/nftoken.md

@@ -54,7 +54,7 @@ Flags are properties or other options associated with the `NFToken` object.
 | `lsfBurnable`     | `0x0001`   | If enabled, the issuer (or an entity authorized by the issuer) can destroy this `NFToken`. The object's owner can always do so. |
 | `lsfOnlyXRP`      | `0x0002`   | If enabled, this `NFToken` can only be offered or sold for XRP. |
 | `lsfTrustLine`    | `0x0004`   | **DEPRECATED** If enabled, automatically create [trust lines](trust-lines-and-issuing.html) to hold transfer fees. Otherwise, buying or selling this `NFToken` for a fungible token amount fails if the issuer does not have a trust line for that token. The [fixRemoveNFTokenAutoTrustLine amendment][] makes it invalid to enable this flag. |
-| `lsfTransferable` | `0x0008`   | If enabled, this `NFToken` can be transferred from one holder to another. Otherwise, it can only be transferred to or from the issuer. |
+| `lsfTransferable` | `0x0008`   | If enabled, this `NFToken` can be transferred from one holder to another. Otherwise, it can only be transferred to or from the issuer. The transfer to the issuer must be via a buy offer created by the issuer and not a sell offer from the holder of the `NFToken`.|
 | `lsfReservedFlag` | `0x8000`   | This flag is reserved for future use. Attempts to set this flag fail. |
 
 `NFToken` flags are immutable: they can only be set during the [NFTokenMint transaction][] and cannot be changed later.