No, the miles required and taxes charged is system generated, not manually. Let me share with you some history ok...

I made some dummy bookings since 31 Oct to KrisFlyer with 2 itineraries. The 2nd itinerary is SIN-TPE-CTS-HIJ-NRT-SIN. This one cannot be booked because of backtracking from HIJ-NRT. Furthest point is CTS. NRT is higher point to SIN compared to HIJ. Need a separate ticket for CTS-HIJ-NRT. I ask if SIN-TPE-CTS-NRT-SIN need how many miles. The agent said 55,000 miles.

So on 31 Oct I booked SIN-TPE-ICN-HIJ-NRT-SIN, agent said 55,000 miles, but I did not issue the ticket. The seats were taken away few days later. (ICN is lower point from SIN, 2880 miles, HIJ is higher point from SIN 2950 miles, NRT is highest point 3300 miles, so ok). I confirmed with agent really 55,000 miles and not 80,000 miles? She checked the table and replied: by right need 80,000 miles, but system say 55,000 miles den 55,000 miles, cannot correct the system.

On 05 Nov, I booked the same itinerary again. Agent said 55,000 miles, but I did not issue the ticket again. Still hestitating. Seats taken away a few days later.

Finally, I decided to go ahead with the trip and booked again on 10 Nov and issue ticket on the spot.

That's the whole history of it.