Be careful with the units quoted.
My bottle of Nattokinase indicates 100mg = 2,000FU (Fibrinolytic Units).
It looks like you might have confused the units.
A Nattokinase dose is usually quoted in Fibrinolytic Units not in Milligrams (big difference) be careful.
400mg (4 capsules) would typically give you 8,000FU
Cheers