Yes, that phrase is definitely doing some work here :). The followup might be "the total of what?" +1 to sibling post on proper bookkeeping but we can also sum inflow/outflow for each of the entities. There isn't a node where it makes sense to add +$27 and +$2.

The customers collectively are at -10*3 + 1*3 = -$27. The hotel is at 10*3 - 5 = $25 The bellhop is at 5 - 1*3 = $2

And those sum to zero for the system; no money was created or destroyed.

Or, thinking in terms of physical bills, the bellhop's two dollars are a subset of the 27 the customers paid out and adding them is double-counting. The real math behind the problem is just 27 = 25 + 2.