As I mentioned previously, I had presumed that you already had processed a WT through Off-Cycle to give an Advance to an employee, and that it was posted to FI/CO.
If nothing is done yet, then you should first query what will be your Business Process.
If the Advance is processed through Payroll (Regular or Off-Cycle) and generates a payment to the employee, then the WT should be mapped to FI/CO. And to make a payroll deduction for the reimbursement of the advance you could use the same WT in negative, but it is better to have a distinct WT.
As for Off-Cycle Adjustments, if all you want is to keep a record that the employee received an Advance directly from Finance or reimbursed money directly to Finance, then you would require different types of WTs since these should not have any impact on net pay.
Any IT0015 should be processed through Payroll. A negative deduction will generate a reimbursement (payment) just as a negative payment should generate an Arrears or a Claim.
Any Advance or Reimbursement should be posted to Finance, but when the exchange is done outside of Payroll then Ledger Entries are usually required.