I am planning on transferring Citi TY Points to KrisFlyer to book one leg of my honeymoon.

I know you get 15% discount for booking online (as long as your flight and any connections are on Singapore metal), but my question is:

Do I need to have 100% of the points in my KrisFlyer account, or can I just transfer the 85% needed?

e.g. - the flight I'm looking at is 85,000 saver level. Do I need to have all 85k in the account and they will only charge me 72,250 for the flight, or can I transfer 73k and still book?

The reason I ask is if I have to transfer all 85k, and save 15%, then those 13k miles are just sitting there (with no immediate plans of using them in the near future) instead of being available to transfer to another partner.