Confused About the Lit maga

[Gin Fenrir]

So if I equip a lit maga, will my rank 7 skill be boosted by 90% too?

[Moriya Suwako]

That is correct.
Literature magatama increases all rank 1+ skill force by 90%, it means all skills that are above said rank will have their skill force increased by 90% in which does include rank 7 skills.