"Hi Gillian,
Thanks for visiting my site and for the email
Re Hi G and Low G setup,
It is referring to how people would like their strings.
Some people prefer the standard re Entrant Tuning, ie the g and A strings are thin, and the C and E strings are thick,
this is whats generally called a "High G tuning"
The other string tuning is Linear tuned, ie the A is the thinnest, the E thicker, the C thicker again and the G thicker again, also called Low G Tuning.
Both are used with standard ukulele Chords, so no re learning,
but the real difference is the Low G string provides a BIG Bass tone,
where as on the High G tuning its so much more jangly and trebly sounding (The C string is as low as it goes in Bass tone).
Ukuleles generally come standard as High g Tuning, but it is a very popular option to restring for Low G Tuning.
Just sold my last Concert so I am currently out of stock, but that should be rectified within the next month when another shipment arrives at the Aussie Wholesaler.
Cheers CC