Not quite. Your Magic allocated towards your mage powers determines things like what spirits may be summoned, when you are overcasting, and so on, but you use your full Magic for things that
don't involve spellcasting/summoning
or adept abilitites - here's what the FAQ has to say on the subject.
QUOTE (From the FAQ:)
Though mystic adepts must split their Magic between Magic-based skills and adept powers, it says that for all other purposes, including the limits of adept powers, the mystic adept uses his full Magic attribute. Does this mean that a mystic adept with Magic 6 who has allocated 2 points to Magic skills and 4 points to adept powers can cast Force 6 spells without flinching?
The Magic points allocated towards Magic-based skills counts for all aspects of those skills. This includes: Magic-linked skill tests (Summoning, Spellcasting, Enchanting, etc.), overcasting, and maximum spell Force, for example.
For power points and Magic when used by adept powers, only the points allocated towards adept powers apply. This includes Attribute Boost Tests and the like.
For all other purposes -- i.e., non-Magic-linked skills -- the mystic adept's full Magic attribute is used: pressing through astral barriers, initiation grade limit, Masking metamagic, and so on.
So in the example above, the maximum Force he can cast at is 4, and anything over Force 2 is Physical Drain.