tarek got it right. The answer is "Tennis Grand Slams" or "Grand Slam Tournaments" (but the latter could be confused with the Golf ones)...
The numbers are indeed time differences, relative to the standard Eastern time in Australia. Paris and London are 8 & 9 hours behind respectively, and New York is 14 hours behind, or effectively 10 hours ahead less a day. Melbourne is in the same time zone but when the Aussie Open is held, the Daylight Saving is on so the time is effectively 1 hour ahead.
It's handy for us as a time zone reminder - Roland Garros, Wimbledon and Flushing Meadows are 8, 9, 10 hrs apart from us respectively. As for ahead of behind, just remember that in terms of Davis Cups success, US is the only one ahead of us while France and Britain are behind...
Well done tarek!