  It was found that the canonical energy of multi-brane solutions in CSFT
constructed by the KBc algebra has a symmetry under the exchange of K=0 and
K=\infty (inversion symmetry). On the other hand, the gauge invariant
observable (GIO), which is regarded as the energy defined by the gravitational
coupling of open string, cannot count the energy from K=\infty and therefore is
not equal to the canonical energy. To resolve this discrepancy, we examine the
recent argument of Baba and Ishibashi which directly relates the two energies.
We find that the gravitational coupling which is equivalent to the canonical
energy consists of the GIO and another new term, and the whole has the
inversion symmetry.
