Context installation

The context installation page contains 6 text-input boxes, each followed by a check box.

I’ve read the guiding instructions there, but it’s not clear.

What is the difference between if I accept the auto-determined settings and

a. leave the check box empty
b. put check in box.

It would seem these two result in the same outcome. The instrustions seem to suggest otherwise.

If I CHANGE/modify one or more of the auto-determined settings, but do not put a check in corresponding box, what happens?

Thanks.