General is NOT a timing its a lower frequency, it behaves more like the different frequency's on a VLF.
And the Ground modes affect how the detector's tracking works, Difficult basically holds more ground info for longer whereas Normal updates and erases certain info quicker.
READ THE MANUAL then read it again.
The timings on the GPX detectors change the RX waiting/receiving times, an entirely different process, this cuts out a lot more info.
Its not my intent to be patronizing with the read the manual comment.
I seriously think everyone should read the manual more.
I must have read mine more than 200 times now, there is a wealth of information in there