I think I have found a bug in custom time zones. When I enter GMT + 8 as +60 x 8, the numbers seems to come out back wards. I enter -(minus) 60 x 8 ad it seems to work OK.
Maybe I didn't understand you but when I tried to enter 480 to create a custom time zone the numbers didn't come out backward. Could you make some screenshots illustrating this issue before and after you make these changes?