*Payment Type = fixed value
*Description = Security Deposit||[IF<=:[INVOICEFIRSTITEMNUM]:800:200|[INVOICEFIRSTITEMNUM][/.0]4]
(Security Deposit is the description, then 2 | symbol, then the calculation for the 'Amount' to be set.
This calculation, tests if the first invoice item value (usually the Accommodation value) is greater than or = 800 if so set the Security Deposit Amount = 1 quarter of the first invoice item value, otherwise set = 200.