Complex sentence: When a Creditrans is validated, the amount subtracted from its denomination is variable depending on the transport used, when using two transports in a row (for instance Underground and bus) a 20% discount is applied on the second trip.
Split into simpler sentences: When a Creditrans is validated, the amount subtracted from its denomination is variable depending on the transport used. Also, when using two transports in a row (for instance Underground and bus) a 20% discount is applied on the second trip.