Settings for Autotrol 255? Hardness? Capacity?

I'm sure this is a silly question....but.........

Purchased a house with a Autotrol 255 Valve/460i softener. The house has been empty for nearly 8 years (seasonal home).
We have hard water in our area but not what I call overly hard.....no real iron, but lime is an issue.

What would you sugguest I start out with the hardness setting? The range is 1 to 99. I understand that hard water is 8.7 to 14.6 grains per gallon.......but what do I set this softener at for starters?

After that where do I set the capacity setting? (1 to 99)
Can someone give me a good place to start?
I have the manual, but I'm lost at the hardness and capacity settings.

It won't regenerate on its own, but will with the manual button. I'm assuming I need to clean the injector screen and injector.

Kate

A water test is needed. One needs to know the hardness of the water that the unit is dealing with.
How is it that the water has an 8.7-14.6 grain reading?
Capacity is based on the amount of media or resin and the amount of salt that is used each time that the system regens or cleans.