Hi Dominic,
When we use count in the Get_REST_Value command, we operate with nodes and not with a node's values.
In your case, you use JSONPath ngbAlerts, so you are looking for ngbAlerts node. There is only one node ngbAlerts, that is array of 2 objects, but still only one node.
If you wants to get number of the element in array, you need to use array element related field, for example, ngbAlerts.alertGraphicUrl
Regards,
Subject7 Team