I'm asking because when I disenchant an item, the enchantment shows a stat such as "10% frost damage". However, when I disenchant the item to learn its effects and apply them to another item, the effect reduces to far less than 10%.
Level up your Enchantment skill, use Enchantment potions, buy enchantment Perks.
When you disenchant an object, you learn the "flavour" of enchantment, not the strength. A "1% Frost Damage" weapon and a "100% Frost Damage" weapon are exactly the same enchantment, just cast at different proficiencies.
The Enchantment skill maxes out at 100, although you can boost it beyond that with Fortify Enchantment Potions, Seeker of Sorcery, or Ahzidal's Genius. The "Enchanter" Perk can be purchased up to 5 times, each level giving a +20% boost. Element-specific Perks exist, such as "Frost Enchanter" making Frost enchantments 25% stronger.
It is worth noting, however, that while disenchanting a strong or weak enchantment of the same type will give you the same Enchantment to use, disenchanting the stronger item will give your more Enchantment experience. Since each Enchantment can only be obtained once by disenchanting, this is worth considering if you have multiple items with the same enchantment.