Theoretical and actual MA
Ideal Mechanical Advantage (IMA) is the predicted MA assuming that all losses in the system can be ignored. We assume that all pulleys are 100% efficient and that ropes running over objects such as edges and carabiners experience no friction.
Theoretical Mechanical Advantage (TMA) is what we can calculate when we attempt to model and include losses in the system. We may make broad assumptions and attribute frictional losses to components and changes in direction of ropes.
Actual Mechanical Advantage (AMA) can only be measured during the operation of the system. It cannot be predicted however, with careful consideration, it should be fairly consistent with the TMA.
The following image shows a range of scenarios assuming 50% loss through carabiners and 5% through pulleys.