Details on the machine: 64,000 gr capacity, 2.0 cu/ft resin (standard resin)

I need some help setting up the machine to give me good salt efficiency. I probably won't be needing the whole 64k capacity right now.

I have 3 adults in the home using about 75 gal/ per day so that's 225 gal.

Hardness is 22 and I would like to regenerate every 9-10 days. I was thinking of setting the capacity of the machine at 40k. Am I thinking of this correctly?

Here is a link to the install guide and settings that I used for programming:

Current settings:

VT: St2b (Standard Downflow/Upflow Double Backwash)
CT: Fd (Meter Flow Delayed)
C: 64k (capacity)
H: 22 (hardness)
RS: SF (Percentage Safety Factor)
SF: 20 percent
DO: 10 (Day override)
RT: 2:00AM
BW: 10 mins (back wash)
BD: 60 mins (brine draw)
BD: 40 (salt time setting)
RR: 10 mins (rapid rinse)
BF: 10 mins
FM: t1.2 - 1.5'' Turbine Meter (7000 default)