Another confusing example is the connection between Metro 3 and RER A lines in Paris.
Between Opéra and Havre-Caumartin, line 3 is just above Auber A station. The line diagrams in M3 trains indicate that going westwards, passengers shouls change for line A at Opéra, and that eastwards travellers should change at Havre-Caumartin.
The idea is fairly simple, assuming that both connections require the same time (which is not totally true), it looks wise to change at the first interchange.
Some people occasionally forget this and get into trouble: at Opéra (eastwards) or Havre-Caumartin (westwards), the connection with RER A is NOT indicated (although it can be reached!)