I checked on the calculator as well. If you have a super snow, it has to be a Mack snow, because Gem snows do not produce super snows (according to the reptile calculator). However, Gem snows can produce supersnows if bred to a Mack snow. So if you breed a Gem snow to a super snow, the offspring that get the Gem snow gene will also get a Mack snow gene and will be super snows (and also Mack snow hybrids). The offspring that don't get the Gem snow gene from that parent will get a Mack snow gene from the super snow parent and will be Mack snows. The reason you won't get anything called "Gem snow" is because every offspring that gets the Gem snow gene will also be getting a Mack snow gene from the supersnow parent and will be a super snow,
I guess technically that if your super snow was a hybrid (1 Gem snow gene and 1 Mack snow gene) you could get an offspring that got a Gem snow gene from each parent and would therefore be a Gem snow, but not a super snow (because 2 Gem snow genes does not result in supersnow). However,, you'd have no way of knowing whether the offspring was a Mack snow or a Gem snow unless you bred it to a Gem snow and got super snows (which would mean that the gecko in question is a Mack snow).
Aliza