The number after the name of the effect indicates the level of spells it works up to.
EE4, 4 means it works up to level 65 spells.
4 - up to level 65 spells
3 - up to level 60 spells
2 - up to level 44 spells
1 - up to level 24 (?)
I think EE adds 15% of duration to buffs.