This amount is the trust account balance for a client that will automatically be maintained by the "Evergreen" process in Time59.
Whenever an invoice is produced (and Invoice Trust Request is set to "Evergreen" in User Preferences) and a client's trust balance has fallen below the "Replenish Trigger Amount", a line item will automatically be displayed on the invoice requesting an amount that will bring the client's trust account balance back to the "Required Trust Amount".
For example...
If a client has a Required Trust Amount set at $1000 and a Replenish Trigger Amount set at $500 and a trust balance of $406 then a line item will appear on the client's invoice requesting $594 to bring the trust balance back to $1000. This will be completely automatic. Of course you can adjust the Required Trust Amount and Replenish Trigger Amount at any time.
You may also contact us using the Feedback form or at support@time59.com.