Clarify anchor_asset field (#370)

ecosystem/sep-0001.md

@@ -123,7 +123,7 @@ max_number | int | Max number of tokens, if there will never be more than `max_n
 is_unlimited | boolean | The number of tokens is dilutable at the issuer's discretion
 is_asset_anchored | boolean | `true` if token can be redeemed for underlying asset, otherwise `false`
 anchor_asset_type | string | Type of asset anchored. Can be `fiat`, `crypto`, `stock`, `bond`, `commodity`, `realestate`, or `other`.
-anchor_asset | string | If anchored token, asset that token is anchored to. E.g. USD, BTC, SBUX, Address of real-estate investment property.
+anchor_asset | string | If anchored token, code / symbol for asset that token is anchored to. E.g. USD, BTC, SBUX, Address of real-estate investment property.
 redemption_instructions | string | If anchored token, these are instructions to redeem the underlying asset from tokens.
 collateral_addresses | list of crypto address strings | If this is an anchored crypto token, list of one or more public addresses that hold the assets for which you are issuing tokens.
 collateral_address_messages | list of message strings | Messages stating that funds in the `collateral_addresses` list are reserved to back the issued asset. See below for details.