Add description for MPT MaximumAmount (#2928)

* max amt

* improve comment

Author: shawnxie999

docs/references/protocol/transactions/types/mptokenissuancecreate.md

@@ -44,7 +44,7 @@ This example assumes that the issuer of the token is the signer of the transacti
 | `AssetScale`      | number              | UInt8             | (Optional) An asset scale is the difference, in orders of magnitude, between a standard unit and a corresponding fractional unit. More formally, the asset scale is a non-negative integer (0, 1, 2, …) such that one standard unit equals 10^(-scale) of a corresponding fractional unit. If the fractional unit equals the standard unit, then the asset scale is 0. Note that this value is optional, and will default to 0 if not supplied. |
 | `Flags`           | number              | UInt16            | Specifies the flags for this transaction. See [MPTokenIssuanceCreate Flags](#mptokenissuancecreate-flags). |
 | `TransferFee`      | number             | UInt16            | (Optional) The value specifies the fee to charged by the issuer for secondary sales of the Token, if such sales are allowed. Valid values for this field are between 0 and 50,000 inclusive, allowing transfer rates of between 0.000% and 50.000% in increments of 0.001. The field _must not_ be present if the tfMPTCanTransfer flag is not set. If it is, the transaction should fail and a fee should be claimed. |
-| `MaximumAmount`   | string              | UInt64            | (Optional) The maximum asset amount of this token that should ever be issued, as a base 10 encoded string. For issuances that do not have a maximum limit, set this value to 9,223,372,036,854,775,807 (2^63-1). |
+| `MaximumAmount`   | string              | UInt64            | (Optional) The maximum asset amount of this token that can ever be issued, as a base-10 number encoded as a string. The current default maximum limit is 9,223,372,036,854,775,807 (2^63-1). _This limit may increase in the future. If an upper limit is required, you must specify this field._ |
 | `MPTokenMetadata` | string              | Blob              | Arbitrary metadata about this issuance, in hex format. The limit for this field is 1024 bytes. |
 
 ## MPTokenIssuanceCreate Flags
@@ -58,6 +58,6 @@ Transactions of the MPTokenIssuanceCreate type support additional values in the
 | `tfMPTCanEscrow`   | `0x00000008`     | `8`           | If set, indicates that individual holders can place their balances into an escrow. |
 | `tfMPTCanTrade`    | `0x00000010`     | `16`          | If set, indicates that individual holders can trade their balances using the XRP Ledger DEX. |
 | `tfMPTCanTransfer` | `0x00000020`     | `32`          | If set, indicates that tokens can be transferred to other accounts that are not the issuer. |
-| `tfMPTCanClawback` | `0x00000040`     | `64`          | If set, indicates that the issuer can use the Clawback transaction to claw back value from individual holders. |
+| `tfMPTCanClawback` | `0x00000040`     | `64`          | If set, indicates that the issuer can use the `Clawback` transaction to claw back value from individual holders. |
 
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