Communion Rituals

I don't know how the math is supposed to math when it comes to the soul multipliers, but I know I am getting the proper amount when I do NOT use Multiply glyphs.

I just hit 90 Necro and opened up my Um Ritual Site fully. I selected Greater Communion and saw 120 for the Spirit Memento. I then placed six Multiply II glyphs and it raised it to 177. (All stated numbers from calculations will be based on the Spirit Memento)

Now, does the Multiply glyph work on the original, unmodified 24 souls from the ritual? Is the multiplier additive or multiplicative based on the Leagues amount? Or is it based on the unmodified amount?

Doing the math for the 6 Multiply II glyphs should give 240% more souls, for a total of 408 if it was based on the Leagues rate of souls (That being a base of 400% bonus). If the 240% just works on the unmodified amount of souls, it should add an extra 81 souls, which would bring the total to 201 souls.

Please, someone let me know if I am incorrect in my thinking l, if I missed something, if my math is wrong, or anything. I am just absolutely, completely STUMPED on how 120 souls + 240% = 177.