What is this? (+X eff.)

[Tasidar]

Many stats seem to be shaved down by this (.eff) score in parenthesis. Why is this?

[Effigy]

Some stats (spellpower, defense, saves, etc.) have diminishing returns. The "eff" value you see on items tells how much your stat is increased after diminishing returns. Check the wiki for a more detailed explanation.

[Tasidar]

Thank you!