The “wd amount / balance” column shows the requested withdrawal amount at the top, with the current balance (excluding chips that may be on a Ring Game table) + the Promotional Balance at the bottom.
Clicking the “Mark Paid” button does not actually send the money to the player. You have to do that manually. What it does do is remove the chips from the player’s account, and make an entry in the player’s history file. Additionally, if the balance has dropped so far that a Promotional Balance adjustment is necessary, the system will calculate that and make that adjustment as well.
“Insufficient balance” means the player does not have enough chips for you to cash them out in the amount requested. This could be because the player has sat at a Ring Game, or because the transaction has already been processed outside of this page.