Ukes are generally tuned 're-entrant', meaning the G is higher than the C and E. If you're used to other instruments, it seems weird at first.
You'll notice that the G string is thinner than the C and E strings.
You can also tune the G down (low-g tuning), but you'd need a fatter string. I play a baritone-sized uke, but tuned to Low-G GCEA.