Yes it does seem excessive, the only thought I have, is when you were repartitioning, that when selecting the sizes you wanted you unknowingly moved the marker, which has lead to this lose.
You can try and run Maxblast again, and see if you can reformat the second Partition, first delete this second partition and then recreate it, this might enable you to include the missing GB's.
Aslo check the jumper settings, as sometimes they can be set to overcome a OS system ability to recognise larger hard-drives, Might be worth checking this before, as if this been set or needs setting, then this could have an effect.
When I lost about 8GB, on my drive my old mobo and Bois couldn't handle the size, and when I put in a new mobo, and tried a basic reformat I couldn't retreive the missing GB's, until I change my jumper settings and done another reformat of the whole drive.
I,m assuming that your mobo and Bois are the same as before you reformatted.