I don't use Serebii's IV Calculator. I use the one on PsyPokes.com, which they call DV Calculator. The way it works is this. Select the Pokemon it is, in this case Glaceon. Then select it's level, followed by what it's stats are (HP, Atk, Sp Atk,etc) Then choose the Nature. It will then give you a ball park range of what your Pokemon's IV's are. What you want is 31 in every stat, it will also tell you the max the Stat can be based on the level, Nature, and which Pokemon. For Instance Dialga for Example.
Level 47 with a Modest Nature, the best you can have is this.
165 Hp
118 Atk
132 Def
176 Sp Atk
113 Sp Def
104 Spd
Same Pokemon and Level but Adament Nature
165 Hp
145 Atk
132 Def
144 Sp Atk
113 Sp Def
104 Spd
The Only difference being the Atk and Sp Atk
Keep in mind that these are the highest you can have in each Stat, and the likelyhood of getting them all at the high end in one Pokemon is very rare. It takes a lot of resetting to get them in the higher end of the values.