My take on this is that the total premium is actually S$1243 but
you will only pay S$897 (70% of 1243 is 870. Not sure why there is
27 dollars more).
Your excess is S$250. This means that if any repairs have to be
carried out on your bike, if the amount is >S$250, the cost will
be borne by NTUC fully. However, this would mean that your
insurance premium would increase for the next year (ie >S$897).
So there is a trade-off if your excess is evoked.