Two data elements must be present for velocities to increment.
The AUTH value must be (A)pprove. (AUTH=A)
Velocities only increment within your merchant account. If the orders are linked through another merchant by a common data element, then velocities do not increment; this is called Passive Linking.
VELO and VMAX fields both reference the number of previous transactions. The first transaction for a persona will have a velocity of zero since there were no previous transactions. The second transaction within the same persona timeframe will have a velocity of one since there was only one previous transaction.
VELO = The total number of *previous transactions linking in the persona (over the last 14 days).
VMAX = The maximum number of *previous transactions within any rolling six hour period over the last 14 days.
*The current transaction is not included in the VELO or VMAX count.
In the image below shows that the rule description is Review all orders 2 (Velo), so the intent is to have the rule trigger when there are more than two orders within the persona time frame.
Since velocities reference the number of previously seen transactions, the condition must always be one number less than what is shown in the description.
Best Practice: Type the expected behavior in the rule description field first, then subtract one from this value to use in the rule condition.