Seems I have come across a bug in enchanting unless ZOS has made it this way in 1.6. As an example using a crafted Magicka Armor Glyph either Grand, Splended or Monumental they all give the same Magicka enhancement of 420. Now the Grand Glyph uses Dorado Rune Potency Improvement 7, Splended Rekura Potency Improvement 8 and Monumental Kura Potency Improvement 9. What is the reasoning behind improving a Armor piece of equipment with a higher potency glyph if it will not give a higher value? For ZOS you need to look into this.