Seems fine, although the idea with having exactly 1,3,5, and 7 was to make it more niche as they skipped the evens, the ranges make it more playable. Also I think you're using "it's" rather than "its" which is incorrect in the wording, although we know what you mean.

[hider=proposed Custom SD decklist][b]Custom Structure Deck List:[/b]

[i]Library of Learning.[/i]

Monsters: 15
1 x Fool of Prophecy
1 x Spellbook Magician of Prophecy
1 x High Priestess of Prophecy 
1 x Charioteer of Prophecy
1 x Hermit of Prophecy
1 x Wheel of Prophecy
1 x Justice of Prophecy
1 x Reaper of Prophecy
1 x Temperance of Prophecy
1 x Prophecy Destroyer
1 x World of Prophecy
1 x The Staff of Prophecy
1 x The Ring of Prophecy
1 x The Vessel of Prophecy 
1 x The Blade of Prophecy



Spells 15
2 x Spellbook of Secrets
1 x Spellbook of The Master
1 x Spellbook of Eternity
1 x Spellbook of Fate
2 x Spellbook of Resonance
2 x Spellbook of Wisdom
2 x Spellbook of Equilibrium
1 x Spellbook of Hope
1 x Spellbook of Life
1 x Spellbook of Power
1 x Grand Spellbook Tower

Traps 10
(gm's choice)

Extra 5
1 x Hierophant of Prophecy
1 x Empress of Prophecy
1 x Alchemic Magician
1 x Downerd Magician
1 x Slacker Magician

[/hider]