Leviathan Ex are 100, HM are 95.

If you look closely in the notes you'll see that there are 12 atma's item to collect. What is suspected at the moment is that you will first get an anima weapon, that you will upgrade into an atma, using for example 4 of the 12 atma on it. The 4 atma you pick will determine the 4 stats the weapon is getting. Once those are picked, you can continue upgrading the atma into burtgang, keeping the same stats but increasing the amount bit by bit until you reach i110.