About "the invisible eye revealed"

I have a question about this spell, p157 of ArM5 core rule book.

If my "the invisible eye revealed" spell is level 30.
Can i detect:
A. intellego spells of level 15 or less
B. intellego spells of level 60 or less

I'm really not sure what means "this spell detects the use oif Intellego spells of up to double the level of this spell"?

Up to Level 60.

("This spell" refers to the one immediately in front of you, the one you are reading. So "Level of this" = "Level of IER".)

(Note also that, in English, the phrase "up to" is unclear whether it is meant to include the number, or not - so some readings would say "Level 59 and smaller", and some "Level 60 and smaller" - fun with the English language.)

Thanks Cuchain!