Anyway, according to the Transitlink website:
To qualify for transfer rebates, please ensure that your transfer
is made within the allowed time :
From MRT/LRT to bus, bus to bus, or bus to MRT/LRT, you must
transfer to the next service within 45 minutes of exit from MRT/LRT
gate or from tapping the card on the bus exit card-reader.
For all concessionary travel on buses or trains, the time allowed
for the next transfer will also be 45 minutes of exit from MRT/LRT
gate or from tapping the card on the bus exit card-reader.
The first, second and third valid transfers on a journey must be
made within 2 hours of the first boarding on the same journey.
